Sweat the eggplant so the meatballs hold together. Add the cubed eggplant to a large bowl, sprinkle with kosher salt, toss well, and let sit 20 to 25 minutes until moisture releases.
Transfer the eggplant to a clean kitchen towel, wrap it up, and squeeze firmly over the sink. Open it, fluff it, and squeeze again. This step matters more than anything else for texture.
Heat the oven to 425°F. Spread the eggplant on a parchment-lined baking sheet in an even layer and roast 25 to 30 minutes, stirring once halfway, until browned on the edges and completely soft.
Let the eggplant cool for about 5 minutes, then transfer it to a large mixing bowl. Mash with a fork or potato masher until mostly smooth with some small chunks remaining. Do not puree.
In a small bowl, mix the ground flaxseed with water and let it sit about 10 minutes until thick and gel-like.
Heat olive oil in a skillet over medium heat. Add the diced onion and cook 5 to 6 minutes until soft and translucent. Add the garlic and cook 30 to 45 seconds until fragrant.
Add the tomato paste, Italian seasoning, oregano, crushed red pepper flakes, black pepper, and smoked paprika if using. Stir and cook 1 to 2 minutes until the tomato paste darkens and smells rich. Stir in the coconut aminos and turn off the heat.
Add the onion mixture to the mashed eggplant along with the parsley, flax gel, and oat flour. Mix thoroughly until evenly combined.
Let the mixture rest for 10 minutes so the oat flour can absorb moisture and tighten the mixture.
Scoop a small amount and squeeze it gently in your hand. If it holds together, it’s ready. If it feels loose, add 1 to 2 tablespoons more oat flour, mix, and rest another 5 minutes before testing again.
Refrigerate the mixture for 15 minutes to make rolling easier and cleaner.
Scoop and roll the mixture into 1.5-inch balls and place them on a parchment-lined baking sheet.
Bake at 425°F for 18 minutes, then flip carefully and bake another 10 to 12 minutes until browned and set.
For a firmer, more “real meatball” texture, sear the baked meatballs in a lightly oiled nonstick skillet over medium heat for 1 to 2 minutes per side until lightly crisp.
In a large deep skillet over medium-low heat, warm olive oil if using, then add the minced garlic and cook about 45 seconds until fragrant.
Add crushed red pepper flakes, oregano, Italian seasoning if using, black pepper, and cayenne if using. Stir briefly to bloom the spices.
Pour in the roasted garlic pasta sauce and simmer gently for 8 to 10 minutes.
Nestle the meatballs into the sauce, spoon sauce over the tops, and simmer on low for 8 to 12 minutes. Avoid aggressive stirring; gently spoon sauce over them instead.
Finish with hot sauce if using, tasting as you go. Add lemon juice at the end if the sauce tastes heavy or needs brightness.
Garnish with fresh parsley or basil and serve straight from the skillet, fully smothered and saucy.