My vegetarian chili taste too tomatoey. How do I fix that?

How is your consistency? I would also consider some corn masa mixed with a bit of stock to make a slurry - that will thicken as well as absorb some tomato flavor

Without knowing the recipe, I would say in a separate pan saute some additional onions to put in the chili with the addition of cumin and oregano with the chili powder that you have already added. I am assuming you wanted to just keep the quantity the same as well, or you could add more beans and a little vegetable stock in addition to the aforementioned items.