Heat oven to 325°F. Use plastic film to line an 8 x 8-inch baking pan leaving a 1-inch-long overhang on both ends.
In a large mixing bowl or the bowl of your stand mixer with the paddle attachment, combine a very soft stick of unsalted butter with sugar and almond extract.
Reduce speed to low and add in flour and salt and beat until mixed. Add the nonpareils.
Use your fingers or a spatula to scrape the dough onto a work surface. Knead the dough 4 or 5 times then pat it into the plastic-lined 8 x 8-inch baking dish.