Center rack in oven and preheat to 325 degrees F. Lightly butter an 8-inch square baking pan.
In a food processor add the all-purpose and almond flours, cornmeal, sugar, salt, and cinnamon; pulse to blend. Scatter with chunks of butter; process in long pulses until the mixture resembles coarse cornmeal, scraping bottom of bowl once or twice if needed. Pour in the egg yolk, and process in long pulses until mixture is moist (it will look like grainy, thick, wet sand). Continue processing until dough holds together when pinched.
Turn dough into a bowl. Stir in the almonds. Squeeze dough into small streusel-like morsels, dropping the pieces into the prepared pan. Gently pat the pieces down. (Don't crush the clumps. You just want to start them on the road to sticking together.)
Bake for 34 to 38 minutes or until the top is a deep golden brown. Sprinkle with decorating sugar, if desired. Cool in pan about 3 minutes. Run a table knife around edges of torta; turn out onto wire rack. Invert onto a cutting board. Cut into pieces, and return to rack to cool. If desired, leave uncut and serve as a break-apart sweet.