I love all things lemon and these crunchy oat crumble bars will make anyone a lemon bar fan if you aren’t already! Filled with lemon zest and juice, these zippy bars are bright and lemony with a brown sugar-oat crumble topping does double-duty as both the bottom crust and crumble topping. . . Lemon Crumb Bars . . 8 tablespoons unsalted butter, melted. 3/4 cup brown sugar 3/4 tsp baking powder 3/4 tsp kosher salt, divided 1 1/4 cups old-fashioned oats 1 cup all-purpose flour 2 large or 3 medium lemons 1 (14-ounce) can sweetened condensed milk Preheat the oven to 350°F. Line the bottom and sides of an 8x8-inch baking pan with parchment. Mix melted butter, brown sugar, baking powder, salt, and stir to combine. Add oats and flour, and stir well. Reserve 1 cup of the mixture for topping. Transfer the remaining crumble mixture into the baking pan. Pat into an even layer. Bake until golden, 12 to 14 minutes. Meanwhile, prepare the lemon filling. Wipe out the crumble bowl (no need to ...