1. Drain spinach well, pressing between paper towels.
2. Combine Parmesan cheese, 1 Tbsp. olive oil, and 2 Tbsp. breadcrumbs in a small bowl.
3. Cook onion in remaining 1 Tbsp. hot oil in a medium skillet over medium heat 5 minutes or until tender. Add garlic, and cook 1 more minute. Stir in spinach, and cook 2 minutes or until thoroughly heated. Remove from heat, and stir in salt, pepper, and nutmeg.
4. Place tomatoes in a 9-inch square baking dish. Spoon spinach mixture evenly over tomatoes; sprinkle with breadcrumb mixture.
5. Bake at 400° for 25 minutes or until golden brown. Serve immediately.