Transfer the diced eggplant to a sieve over a bowl and season liberally with salt. Set out at room temperature for 30 minutes as you prepare the rest of the ingredients.
Blanch the tomatoes (if using fresh tomatoes):
Bring a large pot of water to a boil. Add the tomatoes and cook for 5 minutes until the skin splits. Transfer the tomatoes to an ice bath for 5 minutes. Once the tomatoes are cool enough to handle, remove the skins and the cores. Crush lightly with your hands and transfer to a bowl.
Prepare the sauce:
Heat 1 tablespoon extra virgin olive oil in a wide pot over medium heat. Add the onion and cook, stirring regularly, for 6-8 minutes until it begins to soften. Add the garlic and crushed red pepper and cook for 1 minute until fragrant.
Simmer the sauce:
Melt the butter into the garlic and onions. Once frothy, add the crushed tomatoes and mash lightly with a wooden spoon. Season with salt and pepper. Add 1/4 cup of water and bring to a boil.
If using, add the cherry tomatoes to the sauce. Reduce heat and simmer for 35 minutes until reduced and thickened. Taste and season to your preferences.
Cook the pasta:
15 minutes before the sauce is finished, cook the pasta until al dente. Reserve ½ cup pasta cooking water and then drain the pasta.
Cook the eggplant:
While the pasta cooks, heat 2 tablespoons of avocado oil in a skillet. While you wait for the oil to heat, pat the eggplant dry thoroughly with paper towels.
Cook the eggplant in batches in the hot oil for 2-3 minutes per side, stirring occasionally, until browned and crispy all over. Adjust the heat as necessary to prevent the eggplant from burning. Carefully transfer the eggplant to a paper towel-lined plate.
Finish the sauce:
Lightly mash the cherry tomatoes and add the torn basil to the sauce. Immediately add the pasta and a few splashes of reserved pasta water and toss to coat the pasta with the sauce. Turn off the heat.
To serve:
Divide the pasta between shallow bowls and pile the hot eggplant on top. Garnish with more basil leaves, if desired. Enjoy!