Preheat oven to 350 degrees F (175 degrees C). Line 12 muffin cups with paper liners.
Beat butter in a bowl using an electric mixer until smooth and creamy; add sugar and beat until light and fluffy. Add eggs, 1 at a time, to creamed butter mixture, beating well after each addition. Add coconut extract and mix thoroughly.
Mix flour, baking powder, and salt together in a separate bowl. Beat 1/3 of the flour mixture into creamed butter mixture on low speed just until incorporated. Add 1/2 of the coconut milk to butter-flour mixture and beat on low just until incorporated. Beat in 1/3 of the flour mixture, followed by remaining coconut milk, ending with 1/3 flour mixture until batter is just mixed.
Spoon 2 tablespoons batter into each muffin cup; top with 1 strawberry slice. Spoon 1 tablespoon batter over strawberry layer; top with banana slice. Spoon batter over banana layer to fill muffin cup completely.
Bake in the preheated oven until a toothpick inserted in the center comes out clean, 15 to 20 minutes.