For the sauce: begin by adding the olive oil and butter to a large heavy bottomed pot or dutch oven on medium heat. Once the butter has melted, add the onion and garlic. Season with kosher salt, stir, and cook for around 10 minutes or until the onions are translucent and the garlic is slightly browned around the edges. Add the crushed red pepper flakes and the tomato paste and cook for about 5 minutes to caramelize the tomato paste. Add the canned tomatoes, season with kosher salt, and stir to combine. Bring to a simmer and cook for 25 minutes or so. In the meantime, prepare your meatballs.
For the meatballs: begin by combining all the ingredients besides the ground beef and olive oil in a large bowl, and set aside for 5 minutes or so before adding the ground beef. This will ensure the breadcrumbs are hydrated and don't steal any moisture from the ground beef. Add the ground beef, and mix just until combined, being careful not to overwork the meat.
Preheat the broiler setting on your oven to high. Separate the meat into ¼ cup portions, roll into balls between your palms (you should have 12 meatballs), and place on a foil-lined baking sheet for easy clean up . Drizzle with olive oil and place the meatballs under the broiler for around 12-15 minutes, or until browned completely.
Add the cooked meatballs to the sauce, stir to coat, and allow the meatballs to simmer with the sauce for about 10 minutes.
Taste the sauce and adjust for salt and acidity. If it tastes too acidic for your liking, add the honey or thick balsamic vinegar, and stir.
Serve over pasta with extra chili flakes and lots of parmesan cheese.