Bring a large pot of salted water to a boil and cook your pasta according to the package directions. Once it's al dente, drain it and set it aside. I like to save a splash of the pasta water in case I need to loosen the sauce later.
While the pasta boils, I chop my basil, slice the tomatoes in half, and cube the brie into small pieces. Having everything ready before you start the sauce makes the whole process feel so much smoother.
In a large sauté pan, cook the tomatoes with one tablespoon of olive oil and a pinch of salt over medium-high heat for about 2-4 minutes. You want them just starting to blister and burst, not fully mushy. Remove them from the pan and set aside.
Add the remaining olive oil to the same pan and lower the heat to medium. Toss in the brie, garlic, lemon juice, and a quarter cup of milk. Let it melt slowly for 4-5 minutes, stirring occasionally so it doesn't stick.
Pour in the rest of the milk along with the salt and pepper. Whisk in the nutritional yeast if you're using it, and keep cooking for another 4-5 minutes until the brie is fully melted and the sauce thickens slightly.
Take the pan off the heat and stir in the spinach right away. The residual heat wilts it perfectly without turning it mushy or overcooked.
Add the cooked pasta and protein of choice into the sauce, mixing gently so everything gets coated. Then carefully fold in the blistered tomatoes, since they're delicate and can break apart easily.
Top your pasta with freshly chopped basil and any extras you love, like cracked pepper or grated parmesan. Serve it warm and enjoy every creamy bite.