Preheat oven to 375°. Line 2 large rimmed baking sheets with parchment paper.
For cookies:
In the work bowl of a stand mixer fitted with the paddle attachment, cream butter and brown sugar on medium-high speed until smooth and pale, about 1 minute. Add egg, beating well.
In a medium bowl, whisk together flour, cornmeal, baking powder, and salt. With mixer on low speed, add flour mixture to butter mixture alternately with buttermilk, beginning and ending with flour mixture. Using a 1½ tablespoon spring-loaded scoop, scoop batter onto prepared baking sheets, about 2 inches apart.
Bake until lightly browned and a wooden pick inserted in center comes out with a few moist crumbs, about 12 minutes. Let cool on pan for 5 minutes. Remove and let cool completely on a wire rack.
For filling:
In a medium bowl, stir together cream cheese, lemon zest and juice, sun-dried tomatoes, oregano, and onion powder. Place in a resealable plastic bag, and cut one corner tip from bag.
Pipe a heaping 1 tablespoon onto flat side of half of cookies. Top with 1 tomato slice each. Top with remaining cookies, flat side down. Serve at room temperature.
Recipe by Taste of the South at https://tasteofthesouthmagazine.com/savory-cornmeal-tomato-whoopie-pies/