Preheat oven to 325 degrees. Grease and flour a bundt pan.
In a mixing bowl, cream butter, and sugar on medium speed until light in color and fluffy (approx. 3 to 5 minutes).
Add eggs, one at a time, until fully incorporated. Blend in flour, baking powder and lemon extract. Stir in vanilla and 7-Up.
Pour in prepared bundt pan. Tap firmly on counter top to remove air pockets.
Bake for 1 1/2 hours.
Cool completely before removing from pan.