Cover the sunflower seeds in water and soak overnight at room temperature in a small bowl, or soak them in really hot water for 10 minutes, and then drain.
In a medium pot, heat the olive oil over medium-high heat. Cook the carrots, onions, and salt together for about 10 minutes until soft, then add the garlic and cook for 1 more minute.
Scoop the carrot-onion-garlic mix into your blender and add the sunflower seeds, broth, cornstarch, nutritional yeast, and tomato paste. Blend until it’s very smooth, then transfer it back to your pot.
Cook the sauce for about 15 minutes over medium heat, stirring often, until it’s nice and thick. Add in the lemon juice and adjust salt/pepper as needed.
While the sauce is thickening, bring a large pot of water to a boil, then cook your pasta with the cauliflower or green beans together (a nifty pro tip!) for however many minutes the pasta package says.
Drain the pasta and veggies, then mix in all of the sauce to create a thick, cheesy, delicious dinner. Serve your sunflower mac & cheese hot in your favorite bowl. It’s also wonderful as leftovers the next day!