Preheat oven to 400°. Spray a 7-well cast-iron mini cake pan with cooking spray.
In a large bowl, whisk together flour and sugar. Using a pastry blender, cut in cold butter until crumbly. Stir in tomatoes. Stir in ¾ cup cold milk just until combined.
Spoon dough into wells of prepared pan. With floured hands, lightly press dough into wells of pan. Brush remaining 1 tablespoon milk onto biscuits.
Bake until golden brown, 20 to 25 minutes. Let cool in pan for 10 minutes. Serve warm.
Notes
*We used White Lily.
Recipe by Southern Cast Iron at https://southerncastiron.com/sun-dried-tomato-drop-biscuits/