Add 1 tablespoon ground cinnamon, 1/2 teaspoon grated or ground nutmeg, and 1/2 teaspoon kosher salt to the melted butter and stir until combined and the salt is melted. Add1 cup all-purpose flour, 1/2 cup granulated sugar, and 1/2 cup packed light brown sugar and stir with a fork until evenly moistened and a variety of crumb sizes form. Do not mix into a paste of uniform consistency. Refrigerate until the butter firms up, at least 10 minutes. Meanwhile, make the cake.