Preheat the oven to 375°F (190°C). Lightly grease a small baking dish or oven-safe skillet.
Mix the creamy base: In a bowl, beat the softened cream cheese until smooth. Stir in sour cream and mayonnaise until fully combined and silky.
Season it up: Add lemon juice, Old Bay, Worcestershire, garlic, half the green onions, parsley, and cayenne or hot sauce if using.
Mix well. Taste and adjust with a little more lemon, salt, and pepper.
Add the cheese: Fold in 3/4 cup cheddar and all the Parmesan.
Fold in the crab: Gently mix in the crab meat, keeping lumps intact. Don’t over-stir.
Top and bake: Spread into the baking dish.
Sprinkle the remaining cheddar on top. Bake 18–22 minutes, until hot and bubbly with light golden spots.
Finish and serve: Let it sit 5 minutes. Garnish with remaining green onions and a squeeze of lemon.
Serve warm with toasted baguette, crackers, or veggies.