Heat the olive oil in a large pot over medium-high heat. Add the onion and garlic and cook, stirring occasionally, until softened, about 5 minutes.
Add the sausage and cook, stirring and breaking up any large pieces, until cooked through, about 8 minutes.
Stir in the tomatoes, tomato paste, beef broth, oregano, basil, sugar, black pepper, and red pepper flakes. Bring to a boil, reduce heat to low, and simmer, stirring occasionally, until the sauce is thickened, about 45 minutes.
Taste and season with salt, if desired.
Interesting Facts
Bolognese sauce originated in the Italian region of Emilia-Romagna.
It is traditionally served with tagliatelle, a flat noodle.
The sauce is often referred to as ragù alla Bolognese.
It is made with a combination of ground beef, onions, tomatoes, and herbs.