Preheat your oven to 350°F (175°C). Grease and flour a 9-inch round cake pan.

In a small bowl, toss the chopped rhubarb pieces with 0.5 cup of sugar and 1 tablespoon of flour. Set aside.

In a large bowl, cream together the softened butter and 1 cup of sugar until light and fluffy. Beat in the eggs one at a time, ensuring each is incorporated before adding the next. Stir in the vanilla extract.

In a separate medium bowl, whisk together the 1.5 cups of flour, baking powder, and salt. Gradually add the dry ingredients to the wet ingredients, alternating with the milk, beginning and ending with the flour mixture. Mix until just combined; do not overmix.

Gently fold the sugared rhubarb into the batter until evenly distributed.

Pour the batter into the prepared cake pan and smooth the top. Bake for 45 to 55 minutes, or until a wooden skewer inserted into the center comes out clean.

Let the cake cool in the pan for 15 minutes before inverting it onto a wire rack to cool completely.