In a bowl, mash avocado with a fork and stir in tomatoes, green onions, cumin, chili powder, garlic and lime juice; season to taste. Set aside.
In a small bowl, toss cucumber with cilantro. Set aside.
Heat olive oil and butter in a medium pan over high heat. When butter melts, add scallops and cook until slightly browned, about two minutes per side. Divide guacamole among four appetizer plates. Place three scallops on each plate and top with cucumber and cilantro.
Per serving: 193 calories, 9 g protein, '15 g fat (2 g saturated fat), 8 g carbohydrates, 4 g fibre, 16 mg cholesterol, 83 mg sodium