Whisk flour, sugar, baking powder, baking soda, cardamom, nutmeg, and salt in a large bowl.
Cut butter into the dry mixture. Add eggs, yogurt, and milk and stir just until combined.
Knead the dough just until it forms a ball, then cover with plastic wrap and let rest in the fridge for 1 hour.
Heat about an inch of oil in a large flat-bottomed pan over high heat.
While oil is heating, roll the dough out to about 1/8" thick on a well-floured surface.
Trim the edges and cut into 2-1/2" strips. Cut diagonally across the previous cuts into 4-1/2" strips to create elongated diamonds.
Cut a small slit lengthwise in the center of each diamond. Gently pull one end through the slit to create the cruller twist.
Lower kleinur in the hot oil one at a time, working in small batches so the pan isn't crowded. Fry on each side for 30-60 seconds until golden brown, then set on a rack lined with paper towels.
Let cool for about 5 minutes, then dust with powdered sugar and serve warm.