Preheat the oven to 400 degrees Fahrenheit.
In a large bowl, use an electric hand mixer to combine 8 oz cream cheese, ½ cup mayonnaise, and ¼ cup sour cream.
Add the ¼ tsp onion powder, ¼ tsp ground mustard, 1½ tsp Old bay, 1 ½ tsp worcestershire sauce, 2 tsp hot sauce, and ½ lemon juice and mix again until combined.
Add 1 cup of the sharp white cheddar and ½ cup of the gruyere cheese into the bowl along with the 16 oz lump crab meat and mix by hand until folded in.
Place the dip in a cast iron skillet and then top with the remaining ½ cup white cheddar and ¼ cup gruyere. Sprinkle with more old bay if desired.
Bake for 15-20 minutes, until the dip is bubbly around the edges. If desired, you can turn to your oven to a broil and broil the dip for about 1 minute (watch it carefully!!) until the top gets some color.
Top with chopped green onions and serve with crostini, chips, or crackers and enjoy!