1½ pounds rhubarb stalks, cut into ½-inch pieces (about 6 cups)
2 cups organic evaporated cane sugar
2⅓ cups all-purpose flour
½ teaspoon baking powder
⅛ teaspoon fine salt
2 sticks (8 ounces) frozen unsalted butter
2 large egg yolks
⅔ cup whole unsalted almonds, toasted
1. Place the rhubarb and 1 cup sugar in a saucepan over medium heat, stir to combine, and cook until the rhubarb releases some juices, about 5 minutes. Reduce the heat to low and simmer, stirring occasionally, until the rhubarb is soft and just starting to fall apart, about 25 to 30 minutes. Remove to a bowl and let cool.
2. Combine the flour, remaining cup sugar, baking powder, and salt in a large bowl. Grate the butter on the large holes of a box grater, add it to the flour mixture, and rub between your fingertips until the ingredients just hold together when squeezed, about 3 minutes. Add the yolks and combine until the dough forms large, fist-size chunks when squeezed, about 1 minute (the dough will be crumbly). Shape the dough into a flat disk, cover in plastic wrap, and refrigerate for at least 30 minutes.
3. Heat the oven to 375 degrees and arrange a rack in the middle. Coarsely chop the almonds and set aside.
4. Evenly crumble the chilled dough over the bottom of a 13-by-9-inch baking dish, then firmly press it into the dish using your fingers or the bottom of a measuring cup. Sprinkle the chopped almonds over top and press them lightly into the dough. Using a slotted spoon, evenly spread the cooled rhubarb over the base. If you have any remaining syrup, pour up to ⅓ cup over the top. Bake until the dough is brown and the rhubarb mixture is bubbly around the edges, about 40 to 50 minutes. Let cool completely before cutting into 2-inch bars.