Squeeze spinach to remove liquid. With a mixer, beat spinach, mayonnaise, cream cheese, onion, garlic, 1 cup parmesan cheese, and pepper until thoroughly combined.
Mound mixture in a 3- to 4-cup baking dish. Sprinkle evenly with 2 tablespoons parmesan cheese and the paprika.
Bake in a 350° oven until hot in center and lightly browned on top, 25 to 30 minutes.
Serve hot to spread on baguette slices.