Make the dressing. We'll start with roasting our red pepper. Turn broil setting on oven up to high heat and toss your pepper directly on the top oven rack. You can place an empty baking sheet below as the pepper will drip a bit. (You could also do this on a really hot grill.)
Broil and use tongs to flip every few minutes until the skin of the pepper is blackened all over (see picture below). Once finished, take out of oven, place in a heat proof bowl, cover, and let sit for 5-10 minutes.
As peppers are resting, place your raw Onion. chopped roughly, in a blender with your Red Wine Vinegar and let sit until peppers are ready. Since we're using raw onion, letting them sit in the acidic vinegar will cook them just a tiny bit, enough to get that acrid, raw oniony flavor out so it doesn't overpower the dish.
If you try to peel the skin off the pepper right after taking out of the oven, the steam will burn you! Covering the bowl will allow steam to build up, gently cooking the peppers. After the 5-10 minutes, peel the skin off the pepper as best you can (all the black, charred bits should be gone), and get rid of the seeds - we just want the flesh of the pepper. Place in the blender along with your onion, vinegar, and the rest of the ingredients for the dressing and blend until smooth. Season with Salt and Pepper.
Spoon your roasted veggies onto a plate, spoon the dressing over, and rip some cilantro leaves over the top.
