This is by far my favorite crock-pot recipe. It's easy, takes very little prep work, is sooo forgiving and always tastes great. As an added bonus, the leftovers freeze well too!
The original recipe comes from Beth Hensperger's Not your mother's slow cooker cookbook, which is a wonderful cookbook. Below is my adaptation of the recipe with comments, and photos.
You're going to need:
good quality olive oil, about 1/3 cup (Beth says you can use half unsalted butter. I've never tried this.)
1 sweet yellow onion. (Mine comes from our local farm market. They taste so much better than grocery store ones.)
1 clove of garlic.
2 28 ounce cans of whole plum tomatoes. Yes, get the italian ones. It does make a difference and they aren't that much more expensive.
1 6 oz can of tomato paste (Beth only uses half of the can (3 oz) but I never could find a use for the other half of the can and I haven't noticed much difference in the end produce when I use the whole can.)
Salt and Freshly ground pepper.
You need to:
Chop the onion and mince the garlic. Toss these with a drizzle of olive oil (a tablespoon or two) and some fresh ground black pepper in your frying pan and cook until the onions are soft, stirring occasionally. When my husband is cooking these he always "caramelizes" the onions (read: "blackens") which gives them a unique and somewhat sweeter flavor. Go ahead and try it if you're feeling adventerous. It's pretty good. He also adds extra spices at this step - he suggests cumin or oregano. I like to make my sauce plain. It's up to you.
While those onions cook, get out your handy can opener. (Mine is Oxo brand. It's awesome.) Pop open the three tomato cans (two whole tomatoes and one tomato paste) and dump the whole lot into your slow cooker. When your onions are done, add them to the slow cooker along with some salt and another drizzle of olive oil (you want to have a total of about a third of a cup of oil in there now). Cover and cook on low for 4 to 6 hours.
Double check and make sure your slow cooker is plugged in. (Can you tell I've had a problem with this in the past?) Ok. Now go do your thing for the afternoon.
Oh! Hi! Back already? Time flies. Well, your lovely tomatoes have been simmering away all day and I bet they smell delicious (mine do!). Now it's time to break out one of my favorite kitchen gadgets - the immersion blender! If you don't have one, you can use your regular blender to handle this in batches, but I highly recommend you get yourself an immersion blender. They're not expensive and they're sooo useful.
So go ahead and blend away until you've got a nice uniform color and texture (or you get tired of blending, whichever comes first.)
At this point my husband adds a quarter teaspoon of baking soda to cut down on the acid (just stir until it stops fizzing). Beth uses a teaspoon of sugar.
And Poof! Marinara sauce! Use it today or freeze it for next week!
We used ours today to make chicken parmesian bits (chicken pieces coated in bread crumbs and parmesian cheese and fried over top of whole wheat spagetti with tomato sauce and mozzerella).