Cook bacon in a 12-inch heavy skillet over moderately low heat, stirring occasionally, until browned and crisp, 6 to 10 minutes. Transfer bacon with a slotted spoon to paper towels to drain. Pour off all but 2 tablespoons fat from skillet. Add onion, garlic, salt, and pepper to skillet and cook, stirring occasionally, until onion is softened and lightly browned, about 8 minutes. Add cream, tomatoes, and bacon and simmer until cream is slightly thickened, 2 to 3 minutes. Remove from heat.
Cook pasta in a 6- to 8-quart pot of boiling salted water until al dente. Reserve 1 cup cooking water, then drain pasta in a colander. Add pasta and cheese to sauce and toss to coat pasta, adding enough reserved cooking water to thin sauce as desired.
Makes 4 to 6 main-course servings.