Preheat your oven to 350°F (175°C) and grease a 9x9-inch baking dish.
In a medium bowl, combine the chopped rhubarb with 1/2 cup of the sugar. Set aside to let it macerate for about 10 minutes.
In another bowl, mix together the flour, salt, cinnamon, and remaining 1/2 cup of sugar. Stir in the melted butter until well combined.
Add the eggs, vanilla extract, and milk to the flour mixture. Mix until smooth and well incorporated.
Pour half of the batter into the prepared baking dish, spreading it evenly. Layer the macerated rhubarb over the batter, then pour the remaining batter on top.
Bake in the preheated oven for 35-40 minutes, or until the top is golden and a toothpick inserted in the center comes out clean.
Allow the bars to cool in the pan for at least 30 minutes before slicing into squares.