Cut butter or shortening into biscuit flour. Mix in buttermilk, cheese, and garlic powder to form dough.
Mix mayonnaise, mustard, Cajun seasoning, garlic powder, and onion powder into a paste. Fold in lump crab and crushed crackers.
Form crab mixture into patties or balls and cook about 2 minutes per side, until lightly browned.
Flatten biscuit dough in your hand into a bowl shape. Add reserved crab, cooked crab cake, and more crab, then cover completely with remaining dough.
Bake in a 4-inch springform pan or on a lined baking sheet at 360°F for about 13 minutes, until biscuit is cooked and golden.
Top with garlic lemon butter and serve warm.