Heat the olive oil in a large pot over medium heat. Add the onion and garlic and cook until the onion is softened, about 5 minutes. Stir in the oregano and red pepper flakes and cook for 1 minute.
Add the crushed tomatoes, vegetable broth, water, and tomato paste. Bring to a boil over high heat.
Reduce the heat to low and add the lasagna noodles. Simmer until the noodles are tender, about 10 minutes.