Brown sugar highlights the natural nuttiness of the oats in these toothsome tea cakes. Martha made this recipe on Martha Bakes episode 609.
Preheat oven to 350 degrees. Spread 1/2 cup rolled oats on a rimmed baking sheet and bake until light golden and fragrant, 8 to 10 minutes. Cool then transfer to a food processor; process until finely ground. Add flour, sugar, coarse salt, and pepper; pulse until combined. Add butter, and pulse until mixture resembles coarse meal, about 10 seconds. Add 3 tablespoons cold water and pulse until dough just comes together, adding up to an additional tablespoon as needed.
Turn dough out onto plastic wrap, shape into a rectangle and wrap in plastic. Chill for 45 minutes. Transfer chilled dough to a sheet of parchment paper. Sprinkle with remaining Â¼ cup oats and roll into a 10-by-12-inch rectangle. Using a fluted pastry wheel, cut into thirty-two 2 1/2-by-1 1/2-inch rectangles. Sprinkle with flaky sea salt. If dough becomes soft, chill for 15 minutes.
Arrange bars an-inch apart on two parchment-lined baking sheets. Bake until golden, 28 to 30 minutes. Transfer to a wire rack to cool.