Season a large sauce pan with olive oil and heat over medium high heat, until the oil is shimmering.
Add the onions and generously drizzle some more olive oil on top. Sprinkle a generous pinch of salt and then sauté so they are fully coated in olive oil and evenly dispersed in the pan. Mix in the pan so the then let them sit in the pan for 2 minutes, until slightly golden brown. Adjust the heat to medium and sauté and continue to let them develop color for 1-2 minutes. You will notice some golden brown bits on the pan -- that's what we want!
Add about 1/3 cup of water to the pan to deglaze the browned bits off the bottom. Continue to sauté. The water will quickly cook off and the onions will develop a beautiful golden brown color.
Add 2 tbsp of butter to the onions and mix until the butter is melted. You will see more browned bits on the pan, so add some more water to pick up all of the browned bits, and to transfer that flavor and color to the onions. Repeat the sauté and deglazing process for another 5 minutes, then add the garlic and set the heat to low. Cover the pot with a lid.
Just for time management purposes, I chopped my eggplant and combined my spice mixture while the onions were sweating. Usually, you're supposed to have all the ingredients prepped ahead of time, but I think letting the onions do their work while you do yours makes the most sense. This is up to you! Either way, let the onions sweat on super low heat for another 5-10 minutes.
To combine the spice mixture, add the chopped fennel seed, garlic powder, onion powder, paprika and dried oregano in a bowl. Mix until fully combined and set aside.
Remove the lid from the onions and deglaze the pan with water one more time. (By now, the onions should be softer and in a beautiful golden brown buttery mixture.) Add the eggplant, then add the red wine vinegar and mix everything together. Once the red wine vinegar is fully absorbed by the eggplant and onion mixture, add all of the spice mixture, plus 2 tbsp of chopped basil. Mix until combined.
Add the tomato paste and another pinch of salt. Stir in until combined. Cover the pan and let the sauce simmer on low heat.
Fill a large stock pot with water and salt generously. Bring the water to a boil and cook the pasta according to the instructions.
With a slotted spoon or strainer, transfer the pasta to the sauce and lightly mix it together with a spoon. Plate and serve with fresh basil or parsley on top. This really doesn't need cheese, but if you're vibing cheese, be my guest! Serve immediately. Leftovers will keep for 3 days in the fridge, so long as they are covered in an air tight container or with cling wrap.