Preheat oven to 400 degrees. Arrange eggplant in an even layer on a lined baking sheet. Drizzle with 1 teaspoon olive oil and season with salt and pepper. Roast for 25 minutes.
Place onions in a skillet over low heat with 1 teaspoon olive oil. Heat for 40 minutes, stirring frequently, until caramelized.
Prepare pasta al dente, according to package instructions.
Add garlic to onions. Deglaze pan with red wine vinegar.
Toss onion mixture with tomato pasta sauce, pasta and chicken (optional). Top with red pepper flake and basil.
Recipe by Rachel Schultz at https://rachelschultz.com/2018/05/21/caramelized-onion-and-eggplant-pasta/