Cook the pasta according to the package directions. Drain, let cool to room temperature, transfer to a large zip-top plastic bag and seal. Meanwhile, heat the oil in a large skillet over medium heat. Add the onion and garlic and cook, stirring, for 1 minute. Add the asparagus, carrot, mushrooms, and artichoke hearts and cook, stirring a few times, until the vegetables are crisp-tender and the mushrooms release their juices, about 5 minutes. Add the salt and pepper and stir to coat.
If you're stopping here: Let the pasta and vegetables cool to room temperature. Transfer them separately to large zip-top plastic bags or containers and refrigerate for up to 3 days or freeze up to 3 months. There's no need to thaw before continuing.
When you're ready to eat: Transfer the vegetables to a large saucepan and stir in the tomatoes. Set the pan over medium-high heat and bring to a simmer (or reheat both together in the microwave for about 3 minutes on HIGH). Add the fettuccine and simmer for 2 minutes to heat through (or microwave for an additional 2 minutes). Serve topped with the mozzarella.