Preheat oven to 350°F. Spray a 12-cup bundt pan with nonstick cooking spray.
Beat the cake mix, melted butter, eggs, milk, butter extract, and pudding mix until a thick batter forms. Pour into prepared pan.
Bake for 35-45 minutes, or until a toothpick comes out with just a few crumbs. Remove from oven and cool in pan for 10 minutes.
While the cake bakes, melt butter in a saucepan. Stir in sugar, lemon juice, zest, and salt; cook until it simmers. Remove from heat and stir in vanilla.
Poke holes in the warm cake and pour the lemon butter sauce over it. Cool completely before removing from pan and dusting with powdered sugar.
Notes
This cake is best served warm and dusted generously with powdered sugar.