I came across this recipe on ChefSteps. You can use it as you might use cream, as a garnish on soups, or to add a little boost to a pasta or bean dish. Don’t expect it to taste like cream, but it is satisfying. The flavor is savory and has an unexpected depth, despite such simple ingredients.
The soup in the photo is this tomato soup.
This is a flexible recipe: you can easily add more of the lemon juice, olive oil, and/or salt to suit your taste.
Ingredients
3 large onions
2 Tbsp lemon juice
¼ cup olive oil
½ tsp salt
Coat onions with a little oil then roast them in their skins at 400°F for 45–60 minutes, until onion skins are a bit darkened and the onions are soft. I used parchment paper to ease cleanup. Your kitchen will smell delicious! When the onions are soft, remove from the oven and let them cool so that you can get the skins off without burning yourself. 
In the picture above, you can see that the onions got so soft that their centers slipped out. This may be slightly over cooked, but it was still good. Cut in half and remove the skins, then put onions in blender and blend on high until very smooth, about 90 seconds. Add other ingredients, blend briefly, and then use as a savory garnish.
Store it in the fridge for up to a week, and freeze any that you won’t use in that time. Shake, stir, or reblend to get it nicely mixed again after storage.
I’ve recently heard that it is best to avoid blending extra virgin olive oil at high speeds, because it can become bitter. (Apparently the bitter polyphenols are normally coated in oil, but blending the oil into an emulsion can expose the polyphenols to our taste buds more.) I’ve been meaning to do some taste tests, but haven’t gotten around to it, so in the meantime I’ve been adding extra virgin olive oil to blends at the end, and then blending just enough to incorporate it.
