It’s citrus season. The trees are heavy. An amble through my neighborhood right now would send you past oranges, mandarins, tangerines, lemons, and who knows what other hybrids and splices, all sagging on their branches, almost unable to bear their own weight. When we first moved here in the summer of 2012, I couldn’t believe how much fruit was wasted. Who in their right mind could let it just fall to the ground and rot? And yet as I type, my own lemon tree – sequestered away in its little corner of our backyard – is groaning with a load I can’t reach, its thick, sharp tangle of twigs protecting it from an invading ladder.

So when I cast about for a subject to post about this week, you’d think I would have wandered out and reached up, pulling what fruits I could reach down from my own harvest. But lemons aren’t my favorite. Oh I love a fresh, pulpy lemonade. I could eat lemon curd straight out of the jar. And a tiny, hangnail-puckering squeeze into a chicken or a bean dish is almost essential. But if I’m going to celebrate citrus season and its glories, I’m going to go with my favorite: grapefruit.

Sometimes maligned for its stubborn, bitter pith and its curious ability to render certain drugs either useless or too effective, it is my favorite because it is so complex. Sweet, tangy, sour, infernally juicy, it, and not orange juice, is my choice of beverage when I’m sick. I love the smell of the peel under my fingernails. I could eat grapefruit (and have) until my tongue stung and my lips swelled with the tartness.

But if grapefruit is a bit testy as a raw product, it’s equally challenging in a dish. There are (at least compared to other citrus fruits) a paucity of grapefruit dessert recipes out there, which has always seemed like a shame to me. The lovely play of sweet and sour with that beautiful color (I prefer a red grapefruit myself) seems perfect to match with sugar.

Tired of the standard, tried-and-true lemon bar, then, I set out to conquer a grapefruit version. My first time through yielded highly positive results – grapefruit zest and lemon zest in the shortbread crust, just for some extra bright punch, a silky smooth custard layer of pale salmon pink, and a careful dusting of powdered sugar across the top. A few adjustments, a bit less flour, and it would be perfect.

Of course, I didn’t take any photographs of this perfect little bar, because I was only experimenting. Yesterday, when I made the batch to share with you, I learned what can go wrong. You see, the basic recipe for a fruit bar like this is to make a shortbread crust – flour, butter, sugar, a breath of salt and maybe a little flavoring agent or two – and bake it just until it starts to turn a bit golden. Then you let it cool a bit until the butter, now molten, solidifies to make a firm layer. You pour on a mixture of fruit juice, eggs, more sugar, and possibly some kind of thickening agent (cornstarch, in this case), and then carefully lever the quavering thing back into the oven to cook through.

The middle step – letting the crust cool – is important. Yesterday I forgot about that step. Here’s what happens when you don’t: the beautiful, pale pink liquid filling plunges straight down, bursts through the crust, and breaks it up into floating islands of mush. You despair. You yell. You say some words that make you glad the windows weren’t open. Then you put it in the oven anyway, and even though what comes out isn’t exactly what you were intending, it still looks passable and it tastes perfect.

Curiously, as my grapefruit bars baked, the disrupted crust layer floated up above the (apparently) heavier “filling” layer. What came out of the oven looked more like a cake than the bars format I was expecting, but aside from making it a bit harder to cut (the grapefruit filling smooshes out as you press the blade down), they were fairly acceptable. Tangy, sweet, a play of light crunch and velvet curd, and a huff-inducing layer of powdered sugar over the top to keep you from inhaling too fast.

So the directions I’m providing you are what you should do. They will give you the expected format: a layer of shortbread-like crust on the bottom, topped by a thick layer of soft, slightly jiggly essence of grapefruit. Just don’t forget to let the crust cool. Unless you’d prefer, to echo the persnickety challenge of grapefruit itself, my upside down version.

Grapefruit bars

Makes 9×9 inch pan

Crust:

8 tablespoons butter (½ a cup or 1 stick), at room temperature, cut into cubes

½ cup sugar

1 cup all-purpose flour

¼ teaspoon salt

zest of 1 grapefruit (for extra punch in the crust, add the zest of 1 lemon as well)

Filling:

3 eggs

1 cup sugar

zest of 1 grapefruit

1 cup freshly squeezed grapefruit juice (2-3 large grapefruits)

4 tablespoons butter, at room temperature, cut into cubes

2 tablespoons cornstarch

powdered sugar, for dusting

• Preheat the oven to 350F and prepare your baking pan: cut two 15-inch sheets of parchment paper and arrange them in a cross shape, then insert this cross shape into a 9×9 inch baking dish with the edges hanging out. This forms a kind of sling that will help you remove the bars from the baking dish without breaking them apart. Spray the inside of the dish (including the parchment paper) with non-stick spray, for extra insurance.
• To make the crust, place the butter, sugar, flour, salt, and zest into a food processor and let run until the ingredients are combined and begin to clump together a bit.
• Dump and scrape the clumpy crust bits straight into the prepared baking dish, and use your fingers or the smooth bottom of a measuring cup or a glass to gently but firmly tamp the crust down into an even layer.
• Bake at 350F for 15-20 minutes, until it is pale golden brown and has a tender crust. If it puffs up while baking, stab it a few times with a fork to deflate it. Remove from oven and let cool for at least 10 minutes.
• While the crust cools, make the filling. In the same food processor bowl (you don’t even have to wash it; so many of the ingredients are the same), place the eggs, sugar, butter, cornstarch, and grapefruit zest. Whiz to combine.
• Add the grapefruit juice and whiz to combine again. The mixture will be quite liquid and will look curdled, but it will bake up just fine.
• Note: there isn’t quite enough fat in this mixture to emulsify fully, which means if you leave it sitting for a while it will separate. Whir it up once more just before pouring onto the crust, or make and pour on immediately, and it should be fine.
• Carefully pour the filling over the crust, then just as carefully, return it to the oven (the filling will slosh around a bit if you are too hasty about this) and bake for 40 minutes, or until the filling is just set. It may leave the barest sticky bit of grapefruit-y curd on your finger when you test it.
• Let cool completely (seriously), then dust with a healthy layer of powdered sugar, if desired. If you dust it while hot, the bars will immediately absorb all the powdered sugar.
• To slice for serving, use the parchment paper sling to hoist the whole square out of the baking dish onto a cutting board. Trim off the edges if you wish, then use a very sharp knife or a pizza cutter to slice into squares or rectangles of desired sizes. If the knife or pizza cutter gets gummed up along the way, dip it into a dish of hot water in between slices.