Preheat the oven to 225 degrees F (110 degrees C).

Stir all ingredients together (except for beef broth) in a small bowl.

Place tri-tip in a baking pan. Season generously with the spice rub until both sides are completely covered. (Note: the tri-tip can be cooked immediately or transferred to a plate and refrigerated uncovered for up to 8 hours.

Cover pan with aluminum foil and let meat rest for 20 minutes. Remove tri-tip to a cutting board and cut into 2 pieces along where the grain changes direction. Slice meat across the grain and transfer to serving plates.

Transfer the tri-tip to a clean cutting board and let rest 10 minutes (tent loosely with aluminum foil if the kitchen is cold). Cut the roast in half at the center point. Cut each half across the grain into slices about 1/2-inch thick.

Mix beef broth in with the pan drippings and drizzle over the slices.