Preheat oven to 375 F. Fill an 8 qt. stockpot with water and set over high heat to boil. While the water heats,cut the onion and garlic and arrange in a 12” AccuCore sauté pan or baking sheet. Liberally splash the vegetables with olive oil, sprinkle with salt and pepper, and roast in the oven until the onions take on a deep gold color – about 30 minutes.
Peel the tomatoes while the vegetables are roasting. Using a serrated knife, score the bottoms of the tomatoes with a shallow “X” cut. Fill a large prep bowl with ice,add water to cover, and keep this ice bath next to the stove. Working one at a time, drop each tomato into the boiling water for 6 seconds, remove with a slotted spoon and transfer to the ice bath. The skin should cling loosely to the tomatoes and come off with little effort. If it still holds on tight, leave the tomatoes in boiling water for a little longer. Once the tomatoes are all blanched and have cooled in the ice bath, peel them starting at the spot where you scored them and discard the skins. Roughly chop the peeled tomatoes and transfer to a 4 qt. saucepan.
(Leave the large pot of blanching water on the stove and reduce the heat to low to keep it warm for later).
When ready, remove vegetables from the oven and let cool for a few moments. Press garlic against the cutting board with the back of a wooden spoon so the softened cloves squeeze from the skins. Add peppers and roughly chop with onion, and transfer to the saucepan with the tomatoes. Turn heat to medium and add a quarter bottle of red wine. Let tomato mixture come to a light simmer and cook over medium heat for about 20 minutes. The tomatoes will have softened and released much of their liquid. Using the back of the wooden spoon, smash the tomato chunks against the walls of the saucepan so you get a nice rough, chunky sauce. Add a generous pinch of salt.
Increase the heat under the large pot of blanching water you saved. Add a handful of salt and let it come to the boil. Drop spaghetti all at once into boiling water and cook until it is no longer brittle – about 2 minutes. Transfer the partially cooked pasta from boiling water to saucepan with tongs. Increase the heat until the sauce comes to a strong boil.
As the pasta cooks in the tomato sauce, it will absorb the tomato liquid and thicken the sauce. Cook on high heat until the pasta is al dente – another 8 minutes – and the sauce is clinging to the pasta. Remove the pan from the heat, stir in fresh basil leaves and serve immediately.