In a large pot or deep skillet, warm the olive oil over medium heat. Once the oil is shimmering, add the finely chopped onion. Sauté for approximately 3 minutes, or until the onion becomes translucent and begins to soften.
Stir in the minced garlic, cooking for an additional minute. You want the garlic to become fragrant but not browned, as burnt garlic can impart a bitter taste.
Carefully pour in the vegetable broth, increasing the heat to bring the mixture to a gentle boil.
Once boiling, add the fettuccine (or spaghetti) to the pot. Ensure the pasta is fully submerged in the broth. Cook according to the package instructions, stirring occasionally for even cooking. The pasta should be al dente, which usually takes about 8-10 minutes.
After the pasta is cooked to your liking, reduce the heat to low. Stir in the heavy cream, halved cherry tomatoes, chopped spinach, and dried Italian herbs. Mix thoroughly until the spinach wilts and is integrated into the creamy sauce.
Remove the pot from the heat, then fold in the grated Parmesan cheese. Stir until the cheese melts and coats the pasta evenly. Taste and season with salt and pepper according to your preference.
If the sauce has thickened too much for your liking, simply add a splash of vegetable broth or additional cream to loosen it to your desired consistency.
Notes
For an appealing presentation, serve in shallow bowls topped with extra Parmesan and fresh basil.