Bring a large pot of salted water to a rolling boil. Cook the penne until just shy of al dente, about 1 minute less than the package says (9 to 10 minutes). Reserve 1 cup of pasta water, then drain and set aside.

While the pasta cooks, heat the olive oil in a large deep skillet over medium-high heat until shimmering. Add the carrots and cook 2 minutes, stirring once or twice.

Add the broccoli and bell peppers and cook 2 minutes more, then add the zucchini and snap peas and cook 2 minutes more, until all vegetables are bright and crisp-tender.

Push the vegetables to the edges of the pan. Add the sliced garlic to the center and cook about 30 seconds, stirring constantly, until fragrant without browning.

Pour in the heavy cream and add the cherry tomatoes, red pepper flakes, salt, and black pepper. Simmer gently 1 to 2 minutes, stirring, until the cream thickens slightly and the tomatoes begin to soften. Add a splash of pasta water if it gets too thick.

Add the drained pasta, Parmesan, lemon zest, and lemon juice. Toss 1 to 2 minutes over medium heat, adding splashes of pasta water until the sauce is silky and coats every piece of pasta. Remove from the heat, fold in the torn basil, and serve immediately with extra Parmesan.