Season the short ribs with 2 teaspoons of salt, then cover and refrigerate for at least 1 hour or up to 1 day.
In your Dutchess, heat 1 tablespoon of the oil until shimmering. Add the ancho and bird’s-eye chilies and toast over moderate heat, turning occasionally, until they are fragrant and pliable, about 2 minutes. Remove the chilies from the pot and add the onions and garlic. Sauté over high heat for about 4 minutes. Remove the skin from the garlic and add the chilies back to the pot. Pour in beef stock, cover, and simmer until the chilies are softened, about 5 minutes.In a blender, working in batches if needed, purée the canned tomatoes with the onions, garlic, chilies, and warm stock until smooth; season with salt and pepper.
Wipe out The Dutchess. Preheat oven to 350 degrees.
Remove the short ribs from the refrigerator and dry with paper towels. In The Dutchess, heat the remaining 2 tablespoons of oil until shimmering. Add the ribs and cook over moderately high heat, turning, until browned, about 8 minutes. Deglaze the pot with the red wine vinegar, add the flavored broth, and bring to a simmer.
Cover and braise in the preheated oven for about 2 hours, until the short ribs are very tender.
While the short ribs are braising, make the salsa verde.
Quickly blanch the collard greens in a large pot and cool in an ice bath. Remove the greens from the ice bath and squeeze out any excess water.
In a food processor, add garlic, lemon zest, and parsley. Pulse until the garlic is finely minced. After the garlic mixture is thoroughly combined, add the collard greens a handful at a time in short pulses for a chunky and not puréed mix.
Once incorporated, slowly add the olive oil while pulsing the food processor in short bursts to combine without over-blending. Salt to taste and stir in the rice wine vinegar just before serving.
Serve the short ribs in warm corn tortillas, top with the salsa verde, and garnish with sliced avocado and radishes.