In a large skillet, bring 2 cups of water to a boil. Add bell peppers, reduce heat to low and simmer until just tender, about 5 minutes. Remove from pan, drain and set aside to cool.
In a medium bowl, combine ricotta cheese, eggs, olives, walnuts, parsley, basil, lemon zest and black pepper. Mix well with a fork.
Mound into pepper halves.
Sprinkle with Parmesan cheese.
Place in an ovenproof baking dish and add water to 1/4 inch depth in dish to prevent burning.
Bake until heated through, about 20 to 30 minutes. Place under broiler briefly to brown.