Whisk 1 cup flour and white sugar together in a bowl; cut 1/2 cup cold butter into flour mixture with a pastry blender until crumbly. Press flour mixture evenly into the bottom of a 9-inch square cake pan.
Bake in the preheated oven for 15 minutes. Remove to cool slightly, leaving oven on.
Whisk eggs and 2 tablespoons melted butter together in a bowl; whisk in brown sugar, 2 tablespoons flour, baking powder, and vanilla extract. Stir raisins and pecans into egg mixture; pour over the base.
Bake in the preheated oven until top springs back when touched, about 20 minutes. Cool completely before cutting into squares.