Step 1

preheat oven to 350F. Spray a 9x9 square baking pan and line with parchment paper if you want to be able to lift it out for cutting. This is optional.

Step 2

Use a serrated vegetable peeler to carefully peel away the zest from the lemon. You want only the yellow, not any of the bitter white pith.

Step 3

Put the sugar into the bowl of a food processor, along with the zest. Process, scraping down the sides if necessary, for about a minute or so, until the zest is completely incorporated into the sugar.

Step 4

Add the flour, baking powder, and salt into the processor and pulse to combine everything.

Step 5

Add the butter to the bowl. Pulse to combine, maybe about 20 pulses. The mixture should be crumbly with the butter well distributed and in very small pieces.

Step 6

Measure out 1 cup of the mixture and set aside.

Step 7

Whisk together the wet ingredients and add to the dry, mixing just until combined. Spread the batter into the pan, and top with the reserved crumbs. Note: I use my fingertips to make some larger, chunkier crumbs to create a nice texture on the top. Just compress the dry mixture a little between your fingers to make any size crumb you like.

Step 8

Bake for 40-45 minutes, until a toothpick comes out without wet batter clinging to it.