Combine pepper jelly, honey, vinegar and cayenne, garlic and 6 tablespoons butter in a bowl and whisk to blend. Set aside.
Season the shrimp with Cajun seasoning. Heat 6 tablespoons of the butter in a large skillet over medium-high heat. Add the shrimp and cook quickly, until they are translucent, 3 to 4 minutes. (If you prefer, grill the seasoned shrimp until translucent.) Transfer to a     platter and keep warm.

Add the remaining 6 tablespoons butter to the skillet. Cook the onions and peppers over medium-high heat, stirring, until soft and golden. Add the shrimp and the glaze and toss to coat evenly. Serve immediately.