Split and clean the smelts or have the fish dealer do this for you. Cut 5 diagonal gashes on each side of the fish. Sprinkle with salt, pepper, and lemon juice. Cover and let stand 5 minutes.
Roll the fish in flour. Melt the butter in a skillet and sauté the fish until golden brown, about 4 minutes.
Arrange the fish on serving dishes, pour the juice f