Heat broiler. Place peppers, skin-side-up, on foil-lined broiler pan. Broil 4 inches from heat source until skin blackens and blisters. Transfer to a small bowl; cover and set aside for 10 minutes. When peppers are cool enough to handle, peel off skins; cut into 1/4 strips.
In a large saucepan, melt butter. Stir in drained snap peas, corn, dill, and peppers. Add salt and pepper. Mix gently until thoroughly combined and heated through. (Dish may be made up to 4 hours ahead.)
Boiling (instead of using the microwave) will cook this amount of peas most evenly.