Line a rimmed baking sheet with foil; set a wire rack inside.
Whisk garam masala, salt, brown sugar, and MSG (if using) in a small bowl.
Trim any silver skin and excess fat from short ribs and pat dry with paper towels.
Rub all over with 1 Tbsp. oil, then generously coat with dry rub, pressing to adhere (you may not need all of it).
Place on prepared baking sheet. Chill, uncovered, at least 12 hours and up to 2 days (the longer the better).
Let short ribs sit at room temperature 1 hour before baking.
Preheat oven to 250°.
Drizzle 1 Tbsp. oil over meat.
Pour 1 cup water into prepared baking sheet and cover tightly with foil.
Bake until meat is tender (when you tug at a bone, it should feel like it will slip right out), 4–5½ hours (grass-fed beef will cook faster than grain-fed).
Remove short ribs from oven; increase oven temperature to 325°.
Uncover meat. Spread top with raita, then sprinkle with pistachios, gently pressing to adhere.
Drizzle with remaining 1 Tbsp. oil; season with sea salt.
Roast until nuts are golden brown, 30–35 minutes.
Remove from oven; let rest 15 minutes before serving.
Do ahead: Roast (without crust) can be baked 2 days ahead. Let cool (keep covered), then chill.
To reheat, add ½ cup water to baking sheet, wrap tightly, and bake at 325° until warmed through, 30–40 minutes.
