Set a medium 8-inch nonstick skillet over medium-high heat. Lay in half of the tomatillos cut-side down. When they are browned, 3-4 minutes, flip and brown the other side. Remove from the pan and cool.
Scoop the remaining tomatillos into a food processor and pulse several times until evenly chopped — no pieces should be bigger than ¼ inch. Scrape into a medium bowl.
Scoop the onion into a strainer, rinse under cold tap water, shake off the excess, and add to the bowl along with the chipotles.
Without washing the processor, process the roasted tomatillos until smooth. Stir into the fresh tomatillo mixture. Using a small knife, cut the peel from the oranges. Cut sections (supremes) from the oranges by cutting between the white membranes to release segments with no white pith or membrane. Cut each segment into 3-4 pieces and stir them into the tomatillo mixture. Taste and season with salt, usually ½ teaspoon. Cover and refrigerate.