Preheat oven to 180 degrees C. Grease two 12 cup muffin pans and line with paper baking cups.
Beat butter and sugar in a large bowl using an electric mixer until light and fluffy, about 15 minutes. Mix in the eggs one at a time, mixing each until well blended. Stir in the lemon essence. Stir in the flour alternating with the lemon-lime soft drink, just until the batter is smooth. Spoon the batter into the prepared cups, dividing evenly.
Bake in the preheated oven until the tops spring back when lightly pressed, 20 to 25 minutes. Cool in the pan set over a wire rack.