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Arugula-Laced Caramelized Onion Sauce (Slow Cooker)

by Judith Finlayson

Arugula-Laced Caramelized Onion Sauce (Slow Cooker)

Serves 4 / Vegan / Entertaining worthy / Can be halved


I love the bittersweet flavor of caramelized onions but on the stovetop caramelizing onions is a laborious process of slow, constant stirring. Made in the slow cooker, caramelized onions require almost no attention. In this recipe, I have added sugar to the onions to ensure deeper flavor. Serve this luscious sauce over whole wheat pasta, Slow-Cooked Polenta (page 182) or Basic Grits (page 183). Complete the meal with a tossed green salad topped with shredded carrots for a splash of healthy color.



If you’re pressed for time you can soften the onions on the stovetop. Heat the oil over medium heat for 30 seconds in a large skillet. Add the onions and cook, stirring, until they soften, about 5 minutes. Transfer to the stoneware and continue with Step 2.

If you prefer a smoother sauce, combine the arugula with 1 cup (250 mL) of the tomato sauce in a food processor and pulse several times until the arugula is finely chopped and integrated into the sauce. Add to the onion mixture along with the remaining sauce.

If you are halving this recipe, be sure to use a small (11⁄2 to 31⁄2 quart) slow cooker.


Make Ahead

Complete Steps 1 and 2. Cover and refrigerate onions for up to 2 days. When you’re ready to complete the recipe, in a saucepan, bring tomato sauce, miso and caramelized onions to a simmer over medium heat. Add arugula, return to a simmer and
cook until nicely wilted
flavors meld.


   Medium to large (312 to 5 quart) slow cooker

2 tbsp   olive oil   25 mL

6     onions, thinly sliced on the vertical (about 3 lbs/1.5 kg)      

1 tsp   granulated sugar   5 mL

1 tsp    cracked black peppercorns    5 mL

1 tbsp   white or red miso   15 mL

3 cups   tomato sauce     750 mL

2     bunches arugula, stems removed and chopped (see Tips)       

       Cooked pasta, preferably whole-grain, polenta or grits

1.  In slow cooker stoneware, combine olive oil and onions. Stir well to coat onions thoroughly. Cover and cook on High for 1 hour, until onions are softened (see Tips).

2.  Add sugar and peppercorns and stir well. Place a clean tea towel, folded in half (so you will have two layers), over top of stoneware to absorb moisture. Cover and cook on High for 4 hours, stirring two or three times to ensure that the onions are browning evenly and replacing towel each time.

3.  Remove towels, add miso and stir well to ensure it is well integrated into the onions. Add tomato sauce and arugula and stir well to blend. Cover and cook on High for 30 minutes, until mixture is hot and flavors have blended. Serve over hot whole-grain pasta, polenta or grits.


Get more Slow Cooker recipes in The Vegetarian Slow Cooker by Judith Finlayson