Preheat the oven to 400°. Place the block of cream cheese in the center of a large baking dish. Scatter the tomatoes around the cream cheese, and sprinkle the whole thing with ranch seasoning.
Drizzle olive oil over the cream cheese and tomatoes and place in the oven. Bake for about 35–40 minutes, until the tomatoes are bursting and the cheese is slightly browned on top.
While the cheese and tomatoes cook, bring a large pot of salted water to boil. Cook pasta according to package directions, reserving about ½ cup of the pasta water when you drain it.
Remove the baked cream cheese from the oven, immediately add the shredded cheddar while still hot, and stir well to combine and melt the cheese. Stir in pasta and enough pasta water to make sure the sauce is incorporated with the pasta. Serve immediately.