Slice eggplant in slightly less than 1/2-inch rounds (but not quite 1/4 inch – ruler for reference) and sprinkle both sides with sea salt. Place in a colander in the sink for 20 minutes to drain moisture and draw out any bitter taste.
In the meantime, heat a large skillet over medium heat and add olive oil and the onions. Cook 10-12 minutes – stirring every few minutes. Turn down the heat if browning too quickly. Once caramelized, place in a bowl for later.
Preheat oven to high broil and place an oven rack on the very top rack.
Start pasta water by bringing a large saucepan 3/4 full of water with 1 Tbsp salt to a boil.
Rinse eggplant and dry thoroughly. Arrange on a baking sheet in a single layer and drizzle both sides with olive oil. Broil on high for 3-4 minutes on EACH side until the eggplant is browned (be careful not to burn, just seriously roasted).
Remove eggplant from oven and wrap in foil to steam for 5 minutes. Then peel off skin and add to a blender with almond milk, nutritional yeast, cornstarch and garlic powder. Start with a pinch of salt and add more as you need.
Blend until creamy and smooth. Taste and adjust seasonings as needed, adding more salt, nutritional yeast or garlic powder if desired.
Once pasta water is boiling, add noodles. Cook according to package instructions, then drain and cover with a towel to keep warm.
Pour the eggplant sauce into the same saucepan you used to brown the onions and bring to medium heat. Cook to thicken for about 5 minutes. Once bubbling, lower heat to low/simmer and stir occasionally until noodles are ready.
If topping dish with breadcrumbs, heat a small saucepan over medium-high heat and add olive oil or vegan butter. Than add breadcrumbs and stir. Cook for about 5 minutes until light brown and toasted. Set aside.
Add drained noodles to the eggplant sauce in the large saucepan, along with half of the caramelized onions and stir to coat. NOTE: If your saucepan is NOT oven safe, transfer the mixture to an oven-safe dish at this time.) Smooth the top with your spatula or spoon and top with remaining caramelized onions and the toasted panko bread crumbs.
OPTIONAL: Preheat oven to high broil once more and move an oven rack to the 2nd level from the top. Once hot, place macaroni under the broiler to toast for 1-2 minutes or until golden brown on top. BE CAREFUL not to burn as it can go fast. Don’t walk away.
Remove from oven using an oven mitt and serve immediately. Leftovers don’t tend to reheat well with this dish as the noodles absorb the sauce. Best when fresh.