In a small saucepan melt butter over low heat. Add sage. Cook and stir, allowing the butter to brown to a nutty color. Remove sage. Cool to room temperature.
Remove sausage from casing, if necessary. In a large skillet heat vegetable oil over medium heat. Lightly sear the sausage, stirring and breaking it into small chunks as it cooks. Cook through (but don't allow it to sear too heavily). Transfer to a plate. Cool to room temperature or chill in the refrigerator.
Preheat the oven to 350° F. Butter an 8-inch cast iron skillet or 9-inch cake pan; set aside. In a medium bowl sift together flour, sugar, baking powder, and salt. Stir in black pepper.
In a large bowl whisk eggs and lemon peel about 2 minutes, or until frothy. Stir in flour mixture. Add brown butter. Fold in the sausage, pecorino, and raisins.
Pour batter into prepared skillet. Bake about 30 minutes (if using a cast-iron skillet) or about 25 minutes (if using a cake pan), or until a wooden toothpick inserted into the center comes out clean. Remove from pan; cool on a wire rack. Top with fresh sage leaves, if desired. Serve warm.