2 tbsp finely chopped shallots
2 tbsp white wine vinegar
1 tbsp lemon juice
1 large egg yolk
2 tbsp drained capers
3 tbsp melted unsalted butter
Combine shallots, vinegar, lemon and water. Simmer, stirring occasionally till 2 tbsp remain. Transfer to a blender, add yolk and capers. Blend for 3 seconds. Add heated butter in a stream. Blend sauce till well combined. Add salt and pepper.
Sprinkle snappers with salt. Arrange in a non-stick skillet. Skin side up, top with a lemon slice.
Cook over a moderate heat, 8-10 minutes, tightly covered