Heat olive oil in a large saucepan over medium heat. Add onions and cook, stirring often, until softened, 3-4 minutes.
Add all remaining ingredients except beans and increase heat to high. Bring to a boil, then simmer for about 10 minutes on low heat, or until sauce has thickened. Remove from heat.
Combine sauce and beans in a dutch oven or covered casserole dish. Cover and bake in the oven for one hour, or until beans have reached desired consistency.
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