In a small bowl, mix the granulated garlic with the cumin, 2 teaspoons of salt, and 1 teaspoon of pepper. Season the short ribs all over with the spice mix. Let sit at room temperature for at least 20 minutes and up to 1 hour.
Preheat a grill to HIGH (500 to 600°F) and oil the grate. Grill the tomatoes and onion half, turning occasionally, until tender and charred, 10 to 15 minutes. Transfer to a plate to cool.
Place the short ribs and jalapeños on the grill. Cook (covered if using gas), flipping the ribs and jalapeños every minute, until the jalapeños are tender and nicely charred and the meat is well browned on all sides and registers about 125°F at its thickest part for medium rare, 6 to 8 minutes. (Note: the ribs will be pale after the first flip but will continue to brown as they cook. This cut can overcook quickly, so start checking the temperature of smaller ribs after 6 minutes.) Transfer the ribs and jalapeños to a plate and let rest for at least 5 minutes.
While the steaks are resting, transfer the charred tomatoes and onion to a food processor or blender with the canned chipotle chiles, adobo sauce, chopped cilantro, lime juice, garlic, 1 teaspoon of salt, and ½ teaspoon of pepper. Process until almost smooth. Adjust the seasoning to taste with more adobo sauce, lime juice, salt, and pepper. Scrape into a bowl; you should have about 3 cups of salsa.
Thinly slice the steak and transfer to a large platter. Slice the jalapeños in half lengthwise and arrange on the platter with the steak. Serve with warm tortillas, cilantro sprigs, sliced radishes, and diced onion for garnish. Pass the salsa, sour cream and lime wedges at the table. Enjoy!