Place one 2-inch piece cinnamon stick in a small zip-top plastic bag, seal it, and bang it a couple times with a rolling pin, skillet, or mallet (anything firm and heavy) to break it into small pieces. Place cinnamon pieces, 1/2 cup cumin seeds, 1/2 cup coriander seeds, 2 Tbsp. black peppercorns, 6 cardamom pods, and 1 tsp. whole cloves in a small heavy skillet over medium. Cook, stirring occasionally, until very aromatic and spices are lightly toasted, about 2 minutes. Let cool.
Transfer mixture, in batches if necessary, to a clean coffee grinder and grind into a fine powder. (Or use a mortar and pestle and some elbow grease.) Transfer ground spices to a fine-mesh sieve set over a bowl and sift. Regrind whatever large pieces remain in sieve and add them to the bowl with ground spices. Add 2 Tbsp. ground turmeric. Whisk well to combine. Store in an airtight jar in a cool, dark place up to 6 months. Makes 1 1/4 cups.
