Tomato and Pesto Pasta

My favorite recipe for pasta sauce with pesto. I kinda wing it everytime, so 
this is never quite the same twice.

1/4-1/2 medium RED onion finely diced
 (other onions are fine, but the red is my favorite for this)

Maybe a little garlic depending on how much tomato I put in.

Sweat the onion/garlic in about 3 Tbsp of olive oil & 1/2 tsp salt.

1-2 medium tomatoes, cut coarsely
Throw tomatoes in when the onion is translucent.

Salt & Pepper to taste, but remember you will put in pesto at the end.

Once tomatoes start to break down throw in 1 Tbsp butter & 1/4+ cup coarsely 
chopped basil. Stir that in.

Once the basil wilts put in 1/4+ cup pesto. REMOVE FROM HEAT, or the cheese in 
pesto will stick to the bottom of the pan.

If it looks a little too thick then add a little pasta water to the sauce. 
Stir lightly and you'll have a very nice & creamy sauce that people would swear 
should be in a fancy italian restaurant.

Great over any pasta, but I like it with linguine best topped with a little bit 
of freshly grated cheese.

For variety add seasonal vegetables to this dish. Fresh zuchinni, mushrooms, 
peas, beans, or whatever has a hearty flavor to it would work good.