Preheat oven to 375°F.
Melt the butter in a saucepan over medium heat.
Add the onion, garlic, and pimento peppers and cook for 3 to 4 minutes, until softened and fragrant.
Stir in the jerk seasoning, Cajun seasoning, stock, and lemon juice. Reduce heat to low and simmer for 2 to 3 minutes.
Using kitchen shears, carefully crack the crab leg shells in a few places.
Arrange the crab legs in a baking dish.
Generously brush the crab legs with some of the jerk butter sauce.
Pour the remaining sauce over the crab legs.
Cover tightly with foil and bake for 20 minutes.
Remove from the oven and squeeze fresh lime over the crab legs before serving.