Combine sugar and lemon zest in a bowl. Use your fingers to massage the sugar and zest together until it resembles coarse wet sand.
In a large mixing bowl, measure and add flour, lemon sugar, baking powder and salt. Whisk to combine.
Use a pastry cutter (or a couple of knives or a fork will do) and cut the butter into the flour. Keep going until the butter is no longer detectable in the dry ingredients and it’s a super fine crumb.
Store this cake mix in an air-tight container and refrigerate until ready to use.
If refrigerated, remove and let come up to room temperature for about 30 minutes before using.
