In a small bowl add the minced garlic, 3 tbsp of olive oil, juice of one lemon and salt and pepper to taste. Whisk the marinade well. Add the fish to a baking dish and pour marinade over. Toss the fish around a bit in the marinade, careful as not to break it, cover with plastic wrap and place in the fridge for 30 minutes.
Preheat the oven to 400 F degrees.
Spoon out most of the marinade from the fish and place fish in the oven. Bake for about 15 minutes or until done. While the fish is baking, heat one tbsp of olive oil in a skillet then add the chopped onion and red bell pepper. Saute for about 3 to 5 minutes.
Add zest from one lemon, a bit of salt and pepper and the thawed peas to the skillet and saute for another 5 to 8 minutes. Add the dill, mix well and pour the pea salad into a bowl.
Serve by spooning pea salad on a dish and placing a fish fillet on top.