Cook your pasta in a boiling pot of water for 8-10 minutes, drain.
In a skillet on the stove, add a few splashes of olive oil and saute your onion over medium heat until it is translucent.
Stir in your garlic and your butter, and saute it for about a minute or so.
Get your measuring cup of milk and dissolve a couple of pinches of flour into it. Stir well. Add the salt and pepper to the milk and flour. Now pour the whole thing into the skillet and cook for 3-4 minutes, stirring constantly.
Add your Parmesan or Romano Cheese and stir until completely melted.
Next, stir in the pesto, tomatoes and shrimp. Cook for another 4-5 minutes.
Toss with your linguini and you're good to go. Ready in minutes but tastes like it took hours.