Preheat oven to 325°F (160°C). Grease a 9x5‑inch loaf pan and line with parchment. Whisk together the flour, baking powder, baking soda, and salt.

Beat the butter and sugar with an electric mixer until light and fluffy, about 4 minutes. Scrape down the bowl as needed.

Reduce speed to medium, add the eggs one at a time, then the vanilla. Beat until combined.

On low speed, add the flour mixture in three parts, alternating with the buttermilk in two parts, beginning and ending with flour. Mix just until no flour streaks remain.

Toss the strawberries with the 1 tablespoon flour, then fold them gently into the batter by hand.

Scrape the batter into the prepared pan, smooth the top, and bake for 60 to 70 minutes, until a toothpick comes out with moist crumbs. Cool in the pan for 10 minutes, then transfer to a rack to cool completely. Slice and serve.