Position a rack in the lower third of the oven and turn it on to 350 degrees. Butter the bottom and sides of a 9-inch cake pan, then lay in a round of parchment paper and slather it generously with more butter (about a tablespoon). Sprinkle ½ cup of the pumpkin seeds in an even layer on the bottom of the pan, then sprinkle evenly with 2 tablespoons of the sugar. Set aside.
Measure the remaining 1 ¼ cups pumpkin seeds and 1 cup sugar into a food processor. Pulse the machine a number of times until the seeds are pulverized and resemble damp sand. Add the eggs and the butter and pulse until everything is incorporated. Add the flour, baking powder and tequila and pulse again, just until everything is combined.
With a large knife, chop the chocolate into pea-sized pieces and add it to the batter. Pulse until the chocolate is mixed in—two or three times should do it.
Scrape the batter into the prepared pan and bake until a toothpick inserted into the center comes out clean, 35 to 40 minutes. Let the cake cool for ten minutes, then unmold it onto a serving platter and remove the parchment paper. The cake will have a crunchy layer of candied pepitas on top—which looks even more beautiful with a sprinkling of powdered sugar.