Preheat oven to 325° and grease bottom and sides of a 10" springform pan with butter. Line sides of pan with a 30"-by-2" strip of parchment paper.
In a small bowl, whisk flour, cornmeal, and salt. In bowl of a stand mixer fitted with paddle attachment (or in a large bowl using a hand mixer) on medium speed, beat butter and powdered sugar, scraping down sides of bowl, until butter pieces are no longer visible and mixture is smooth, 4 to 5 minutes.
Scrape sides of bowl. Reduce mixer speed to low and gradually add dry ingredients; mix just to combine. Increase mixer speed to medium and continue to mix until dry ingredients are fully incorporated, 1 to 2 minutes. (Cold butter will collect in paddle; stop and push it out with a rubber spatula.) Add almonds and mix just to combine, about 30 seconds.
Transfer dough to prepared pan. Working quickly so as not to melt butter in dough, press evenly into bottom of pan. Bake until edges are golden brown, about 20 minutes. Transfer pan to a wire rack and let cool.