Bring a large pot of well salted water to a boil. Cook the spaghetti until al dente. Before draining, scoop out about half a cup of the starchy pasta water and set it aside, then drain the pasta.
½ pound spaghetti
While the pasta cooks, heat the butter and olive oil in a large skillet over medium heat. Add the asparagus and cook for about 4 minutes, until bright green and just crisp tender with a little color on the edges.
1 tablespoon butter, 1 tablespoon olive oil, 10 ounces asparagus
Add the red onion and garlic and cook for 1 minute more, until fragrant and softened.
⅓ cup red onion, 2 cloves garlic
Stir in the halved cherry tomatoes, tomato paste, and dried thyme. Season with salt and pepper and cook for about 2 minutes, letting the tomato paste darken slightly and lose its raw edge.
4 cherry tomatoes, 1 tablespoon tomato paste, ½ teaspoon dried thyme, salt
Pour in the heavy cream and the reserved pasta water. Bring the sauce to a boil, then lower the heat to a gentle simmer. Add the drained spaghetti and toss everything together for about 3 minutes, until the pasta is heated through and glossy with sauce.
1 cup heavy cream, ½ pound spaghetti
Taste and adjust the salt and pepper. Serve right away, topped with plenty of freshly grated Parmesan and a scatter of fresh thyme.
salt, Parmesan, fresh thyme
