Cook the spaghetti for 13 minutes, drain, and set aside. If using leftover spaghetti, reheat it.
Preheat the broiler. Heat oil in a medium sized ovenproof skillet not a non stick pan. Add the onion and cook 3 minutes over medium heat. Add diced tomato and cook 3 more minutes. Add the peas and garlic and cook just 1 more minute. Remove from heat.
In a medium bowl beat the eggs together. Add the vegetables. Season with salt, pepper and Reggiano Parmesan cheese.
To the same skillet used for the vegetables, add 1 teaspoon olive oil and spray bottom and sides well with olive oil spray. Heat over medium low heat. Add warm cooked spaghetti to the pan. Pour egg mixture on top and let set on the bottom and through the middle, lifting the bottom occasionally to let uncooked egg run underneath. Once set, after about 5 to 7 minutes, place pan in broiler for 1 to 2 minutes, until top is set. Carefully place a plate on top of pan and flip frittata over onto plate. Slice in four like a pizza and serve.