Preheat the oven to 350°F (175°C). Grease a 9-inch round cake pan and line the bottom with parchment paper.
In a medium bowl, toss the chopped rhubarb with 1/4 cup of granulated sugar. Set aside to macerate for about 15 minutes.
In a large mixing bowl, cream together the softened butter and remaining 3/4 cup of granulated sugar until light and fluffy.
Add the ricotta cheese, eggs, and vanilla extract to the butter mixture. Beat until well combined.
In another bowl, whisk together the flour, baking powder, salt, and cinnamon. Gradually add the dry ingredients to the wet mixture, mixing until just combined.
Fold in the macerated rhubarb, along with any juices that have accumulated.
Pour the batter into the prepared cake pan and smooth the top.
Bake for 40-45 minutes, or until a toothpick inserted into the center comes out clean.
Allow the cake to cool in the pan for 10 minutes before transferring it to a wire rack to cool completely. Dust with powdered sugar before serving, if desired.