Put 1 clove garlic, 1 teaspoon ground smoked paprika, 1 teaspoon ground cumin, 1 teaspoon ground coriander, ½ teaspoon ground fennel and 2 tablespoons finely chopped fresh cilantro into a food processor.
Pulse in short bursts until the garlic and cilantro are finely minced and the spices are evenly distributed, stopping once or twice to scrape down the sides with a spatula.
Cut ½ cup salted butter into chunks and add them to the food processor.
Pulse in short bursts, scraping down the sides as needed, until the butter and spice mixture are well combined and smooth.
Lay a large sheet of cling film on the work surface. Spoon the butter mixture onto the long edge of the cling film in a rough log occupying the center third of the film.
Roll the cling film tightly around the butter to form a compact log, twist or tie the ends to seal, and refrigerate the wrapped log until firm.