Preheat oven to 375°F. Grease a standard muffin tin or line with paper liners—use 12 wells for small muffins or 6 for larger muffins.
Beat butter and sugar until creamy. Add eggs and beat until light.
Stir in water, lemon juice, and carrots.
Add remaining ingredients and stir until moistened.
Pour batter into muffin tins. Bake smaller muffins for 20 minutes and larger for 25-30 minutes, or until a toothpick inserted in the center comes out clean.