In a large bowl, combine 1 (12.5-ounce) can poppy seed filling and 3 large room-temperature eggs.
Add 2 tablespoons room-temperature sour cream, 2 tablespoons melted and cooled butter, 1/2 teaspoon baking soda, 1 teaspoon vanilla, a pinch of salt, and 1 cup all-purpose flour, mixing thoroughly.
Heat oven to 350 F. Scoop cookie dough onto parchment-lined baking sheets. Tamp down with the bottom of a flour-dusted glass.
Bake until cookies are golden brown, about 20 to 25 minutes. Cool cookies on pan.
Dust with confectioners' sugar, if desired. Store in an airtight container.