In a non-stick skillet, measuring 10-inches across the bottom heat the oil over moderate heat until it is hot but not smoking, in it cook the bell pepper rings for 30 seconds on each side, or until they are crisp-tender, and transfer them with tongs to a plate.
To the skillet add the capellini, distributing it evenly and pressing it lightly with a lid that fits into the pan, touching the pasta directly, and cook it, over moderate heat for 25 minutes, or until the bottom is golden. Invert an oiled baking sheet over the skillet, invert the capellini crust onto the sheet, and slide it back into the skillet. Cook the capellini crust, covered, for 10 minutes more.
Spread tomato sauce over the crusty pasta, leaving a 1/2-inch border, and arrange the mozzarella on top. Arrange the bell pepper rings and the pepperoni on the mozzarella and cook the pizza, covered, over moderate heat for 3 minutes, or until the mozzarella is melted. Slide the pizza onto a pizza pan or flat platter, garnish it with the basil, and with a pizza wheel or sharp knife cut it into wedges.
Bring a large pot of water to a boil. Add salt and pasta and cook for 2 to 3 minutes, or until just al dente. Drain and toss with butter, salt, and pepper.