1-First, preheat your oven to 350°F and lightly butter a 9×9-inch square baking pan, or line it with parchment paper for easy removal. This step sets the stage for even baking.

2-Next, stir the lemon juice into the half and half, cream, or buttermilk and set it aside to curdle slightly, which helps with texture.

3-Then, in a mixing bowl, cream the 1/2 cup unsalted butter and 1 cup granulated sugar until it’s fluffy and pale yellow, about 2-3 minutes. Beat in the large egg and 1 1/2 teaspoons vanilla or almond extract until fully combined. Meanwhile, toss the 2 cups thinly sliced rhubarb with the reserved 1 tablespoon flour and set it aside to prevent sinking.

4-In another bowl, whisk together the 2 cups all-purpose flour, 2 teaspoons baking powder, and 1 teaspoon salt. Add half of this dry mixture to the creamed butter mix and blend well, then pour in the liquid mixture and stir again. Finally, add the remaining dry ingredients and mix just until combined, being careful not to overdo it.

5-Now, fold in the rhubarb gently to keep the pieces intact. Pour the batter into your prepared pan and sprinkle the top evenly with the extra 2 teaspoons of sugar. Bake for 40 to 45 minutes, or until the cake is golden and a toothpick inserted in the center comes out with moist crumbs. Let it cool slightly before cutting into slices for the best results.