In a large pan, set over medium heat, add the olive oil. When the olive oil is warm, add the diced Vidalia onions and few generous pinches of salt. Give it a mix and let them cook, covered, for 7 minutes. You really want the diced onions to melt in the pan with the olive oil. I like to make sure the heat is low enough so they slowly cook and don’t brown or burn.
Next, add the minced garlic, crushed red pepper flakes and cherry tomatoes. Cook for an additional 5 minutes, covered, until the tomatoes are softened and have released a lot of their juices. Uncover and cook for an additional 5 to 7 minutes, until it thickens. Turn off the heat while we make the pasta.
Meanwhile, bring a pot of salted water to a boil. Cook your pasta until al dente. I usually cook it about 1 minute before al dente because I like to finish cooking the pasta in the pan with the sauce. Reserve about 3/4 cup of pasta water. Drain the pasta and turn your attention to the pan with the cherry tomatoes.
To the sauce, add about 1/2 cup of pasta water and bring it to a rapid simmer. Cook for about 2 minutes; give it a taste and adjust the salt to taste. I added a few more pinches of salt. Add the pasta in, along with the butter and toss together for about a minute, until completely combined.
Notes
Tips and Tricks:
Fresh cherry tomatoes of the yellow AND red variety are a good combination because the yellow is more tart and bright, while the red tomatoes are more sweet.
Pasta water is your friend. This starch water is a necessary addition with all pasta dishes, in my opinion. It thickens the sauce in the most perfect way.
When buying pasta, look for "bronze-die." While this pasta is always a few dollars more, it means that the pasta is extruded with a bronze extruder. This means that your pasta water will be more starchy and flavorful. And the exterior of the pasta will be ashy and rough - resulting in the pasta sauce adhering to it easier.