Preheat oven to 350 degrees F. Butter a 12-cup standard nonstick muffin tin. In a small bowl, whisk together flour, baking soda, and salt; set aside.
With an electric mixer, cream butter and 2/3 cup brown sugar until smooth, scraping down sides of bowl as needed. Add eggs, one at a time; beat until combined. Beat in buttermilk and vanilla, then flour mixture.
Spoon batter into prepared tin, filling cups about 1/3 full. Place 5 cherries on top of each; sprinkle with remaining 2 tablespoons sugar.
Bake until cakes are golden brown and a toothpick inserted in center comes out clean, 20 to 25 minutes. Let cool 5 minutes in tin. Run a knife around edges; turn out of pan, cherry sides up. Serve warm, with ice cream, if desired.