How to Make It
Preheat oven to 350°F. Sift flour, sugar, cocoa, baking soda, and salt into an ungreased 8- x 8-inch baking pan; spread mixture evenly in pan. Make 1 large well and 2 small wells in mixture in pan. Carefully pour oil into the large well, vinegar into 1 small well, and vanilla into remaining small well. Pour 1 cup water evenly over entire mixture in pan. Stir everything together using a fork until combined.
Bake in preheated oven until a wooden pick inserted in center comes out clean, 25 to 30 minutes. Transfer to a wire rack.
Pour Wacky Cake Frosting over warm cake. Sprinkle with chopped pecans. Cool completely, about 2 hours.