Carmelized Onion and Garlic Pasta

1/4 cup butter
2 large sweet onions, thinly sliced
1/4 tsp crushed red pepper flakes
1/8 tsp salt
8 garlic cloves, minced
4 cups grape tomatoes, halved
1/4 cup balsamic vinegar
1/4 cup olive oil
16 oz angel hair pasta
9 bacon strips, cooked and crumbled
2/3 cup shredded fresh parmesan cheese
1/2 tsp pepper
fresh basil leaves, optional

In a large skillet over med-high heat, melt butter. Add onions, pepper flakes, and salt; saute until onions are tender. Stir in garlic. Reduce heat to med-low; cook, stirring occasionally, for 30-40 minutes or until onions are deep golden brown.

Add tomatoes, vinegar, and 2 Tbls oil. Cook pasta according to package directions. Drain and toss with onion mixture.  Drizzle with remaining oil. Sprinkle with bacon, cheese, and pepper, and heat through. Garnish with basil.