Suggestions for "rice" sauce?

I will be trying my hand at the infamous cauliflower rice tomorrow. I also have a huge stack of mushrooms, so that will be the protein source. All in all, a pretty bland combo.

Does anyone have a good sauce recipe? Preferably tomato or pepper based, as they are in season. Also, the more basic the ingredients are, the better (i.e. no canned soups, condiments like curry, prefer raw tomatoes over tomato sauce etc.).

Cauliflower and mushrooms go very well with the with thyme and rosemary, IMO.  Why don't you add a tsp olive oil to a sauce pan, chop some red bell pepper and onion, sweat them a little (until they are transparent), then add your chopped tomatoes, garlic if you like it, and thyme and rosemary.  Salt & pepper to taste.... Then let everything break down as much as you want (if you want it more "sauce like" let it cook longer) and at the end you can add some crushed red pepper flakes if you like spice.  I make this for a tomato sauce all the time, and change up the spices to match the dish (sometimes I use italian, sometimes herbes de provence...). 

Make some of this

End of the Garden Vegetables

Partly puree it and use it as a sauce.  If you throw in some hot peppers you can make it spicy.