Heat the oil on medium heat in a large pot.
When the oil is hot and shimmering, add the diced onion and garlic. Sauté, stirring frequently, until the onions are translucent. Take care not to burn the garlic and onions. If you do burn this, you will have to start over.
Add the flour and make a roux. At this point it will look like a paste. That is normal.
Add the remaining spices and sauté for 30 seconds.
Deglaze the pot with 1 cup of the water (or broth if not using bouillon)
Scrape the bottom of the pot to prevent scorching when you add the tomatoes.
Add the tomatoes, and chilis in adobo.
Stir to combine, and simmer on low for 20 minutes.
Once the mixture has been simmering for 20-30 minutes, use an immersion blender to blend the sauce.
At this point, taste it and you can add a bit of sugar (2 tsp) if it is too acidic (will depend on the type of tomatoes you use).
Add salt and pepper to taste.
Store in the fridge for up to a week.
Or, store in the freezer for up to 6 months, depending on how you store it.