Preheat the oven to 400°F.
In a large bowl, mix together cream cheese, mayonnaise, and sour cream until smooth and creamy.
Stir in Parmesan cheese, cheddar cheese, lemon juice, hot sauce, salt, and black pepper until well combined.
Gently fold in the lump crab meat until evenly distributed throughout the mixture.
Pour the mixture into a 1-quart baking dish, spreading it out evenly.
Sprinkle the remaining shredded Parmesan cheese over the top of the dip.
Bake in the preheated oven for 25-35 minutes, or until the dip is bubbly and hot.
Remove from the oven and sprinkle with sliced green onions for garnish.
Serve the Hot Crab Dip hot with tortilla chips or crostini for dipping.