1 lb. (4 cups) mixed unsalted nuts (such as cashews, macadamias, walnuts, pecans, or almonds)
1/2 tsp. ground coriander
1/2 tsp. ground cumin
2 Tbs. unsalted butter
2 Tbs. dark brown sugar
2 Tbs. chopped fresh rosemary
1/4 tsp. cayenne
1-1/2 tsp. kosher salt (omit salt if using salted nuts)
Position a rack in the center of the oven and heat the oven to 350°F. Scatter the nuts on a rimmed baking sheet and bake, shaking the sheet a couple of times during baking, until the nuts are nicely toasted, 10 to 15 minutes.
Meanwhile, set a small heavy skillet over medium-high heat. Sprinkle in the coriander and cumin and toast until aromatic, about 30 seconds. Remove the pan from the heat and add the butter, brown sugar, rosemary, and cayenne. Return the skillet to low heat and stir until the butter melts and the sugar dissolves, 2 to 2-1/2 minutes. Keep warm.
Put the nuts into a bowl, pour the warm spiced butter over the nuts, and add the salt. Stir until the nuts are well coated. Taste for seasoning and add more salt if necessary. Let the nuts cool completely.