📖 Instructions

1. First, let's make the rhubarb filling. In a medium saucepan, combine the chopped rhubarb, granulated sugar, water, and lemon juice. Bring the mixture to a boil over medium heat, then reduce the heat to low and simmer for about 15-20 minutes, or until the rhubarb is soft and the mixture has thickened into a jam-like consistency. Stir occasionally to prevent sticking. A lil' tip: if it's too runny, you can add a teensy bit of cornstarch slurry (cornstarch mixed with cold water) to thicken it up real fast.
2. Once the rhubarb filling is ready, remove it from the heat and let it cool completely. While the filling cools, preheat your oven to 350°F (175°C). Line baking sheets with parchment paper.
3. Now, for the alfajores cookies! In a large bowl, cream together the softened butter and powdered sugar until light and fluffy. Beat in the egg yolks and vanilla extract. A stand mixer makes this easier, but hand-mixing works just fine too, just make sure your butter is soft enough. You might wanna add a pinch of salt, too, it balances everything out nicely.
4. In a separate bowl, whisk together the all-purpose flour, cornstarch, and baking powder. Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Be careful not to overmix the dough, or the cookies will be tough. Overmixed dough is the enemy.
5. Turn the dough out onto a lightly floured surface and knead it gently until it comes together into a smooth ball. Wrap the dough in plastic wrap and chill it in the refrigerator for at least 30 minutes. This step is crucial – it prevents the cookies from spreading too much in the oven. I once skipped this and… well, let's just say they looked more like rhubarb-filled pancakes. Still tasted alright, though!
6. After chilling, roll out the dough to about 1/4 inch thickness on a lightly floured surface. Use a 2-inch round cookie cutter to cut out cookies. Place the cookies on the prepared baking sheets.
7. Bake the cookies for 8-10 minutes, or until the edges are lightly golden. Be careful not to overbake them – you want them to be soft and tender. Let the cookies cool on the baking sheets for a few minutes before transferring them to a wire rack to cool completely. They should be fairly pale; a darker color would indicate they're overbaked. If your oven runs hot, start checking them at 7 minutes!
8. Once the cookies and the rhubarb filling are completely cool, it's time to assemble the alfajores. Spread a generous spoonful of rhubarb filling on the flat side of one cookie and top with another cookie, pressing gently to sandwich them together. Don't be shy with the filling! But also, don't overdo it, or you'll have a sticky mess.
9. Dust the assembled alfajores with powdered sugar. This adds a touch of sweetness and makes them look extra pretty.
10. Serve the Rhubarb Alfajores immediately, or store them in an airtight container at room temperature for up to 3 days. They're best enjoyed fresh, but they're still delicious a couple of days later. If you have any left, that is. Heh!