In a large pot, saute onion in olive oil until translucent, about three minutes. Next, add minced garlic, tomato paste, brown sugar, and balsamic vinegar.
Cook for about 30 seconds until fragrant.
Mix in the crushed tomatoes and oregano, reduce heat to medium-low, and simmer sauce for 20 minutes;
In a large pot, bring water to a boil and blanch the cabbage for about a minute and remove the leaves when tender and flexible. Drain them;
Preheat the oven to 350F.