A financier is a French cake traditionally made with ground almonds. For a colorful twist on the classic, try pistachios instead with this recipe from food blogger Beatrice Peltre's "La Tartine Gourmande."
Preheat oven to 350 degrees. Line a standard muffin tin with 8 paper liners or a mini-muffin tin with 24 paper liners, or use silicone muffin molds; set aside.
Using a coffee or spice grinder, grind pistachios into a fine powder; set aside.
In a small saucepan, melt butter over medium heat until light brown in color; remove from heat. Add cardamom pods and vanilla bean and seeds; let stand for 10 minutes. Strain butter; discard solids and set aside.
In a large bowl, mix together pistachio powder, rice flour, cane sugar, poppy seeds, and salt. Beat in egg whites until smooth; quickly stir in melted butter. Divide batter evenly among prepared muffin cups (use 1 heaping teaspoon batter per mini, if using) and transfer to oven; bake until a cake tester inserted into the center of the cakes comes out clean, about 20 minutes for standard size and 12 to 14 minutes for mini. Remove from oven and let cool completely.