Cook pasta in a large pot of boiling, salted water until just tender but still firm to bite, stirring occasionally. Drain well, reserving 1/2 cup of the cooking liquid. Transfer the cooked pasta back to the same pot.

While the pasta is cooking, heat the olive oil over medium-high heat in a large skillet. Add the tomatoes and sauté until beginnning to soften, 3-4 minutes. Stir in the garlic and sauté for 30 seconds, then sprinkle with salt and black pepper to taste. Add the 1/4 cup of reserved cooking liquid to the skillet and scrape up any browned bits. Stir in the marjoram and crushed red pepper.

Pour the sauce into the pot of pasta and add the spinach and Parmesan. Toss to combine, and heat over low eat just until the spinach wilts, 1-2 minutes. Season to taste with salt and pepper and serve. Pass additional Parmesan at the table if you like.