Preheat olive oil in a nonstick stockpot over medium heat.
Add the diced onions and minced garlic, cook over medium heat for 10 minutes, stirring occasionally until the onions are translucent and slightly golden.
Add the smoked paprika, chili powder, cayenne, black pepper, and salt. Stir to combine, then cook for 1 minute so the spices bloom.
Add the tomato sauce, stir to combine. Then add the remaining ingredients: apple cider vinegar, balsamic vinegar, tamari, and maple syrup.
Stir to combine. Bring to a simmer and cook for 10 minutes or until slightly reduced and thickened.
Remove from heat and let cool 15 minutes.
Using an immersion blender, blend the sauce until smooth. You can also use a blender if you do not have an immersion blender.
Pour into a jar and allow to cool. Cover and refrigerate until ready to use.