Preheat oven to 375°. Place sole filets on parchment lined rimmed baking sheet, with a few teaspoons of ghee spread on it. Season sole with salt and pepper and bake in the oven about 5 minutes, or until just opaque and cooked through. Meanwhile, in a small saucepan, melt ghee and add zest and juice of lemon, thyme, capers and salt and pepper to taste. Bring to a boil, whisk and pour over cooked fish. Serve.