Preheat oven to 350 degrees F.
Rub butter inside all of the holes of 12 inch muffin pan. (Or line with paper liners, but I like mine without this. It gives them a very clean look.)
Whisk together the almond flour, teff flour, cornstarch, sugar, and salt. Whisk in the egg whites vigorously until the batter is smooth, then whisk in the melted, cooled butter in 3 additions. Whisk in vanilla. Fill each muffin cup a little more than 1/2 full with batter.
With a fork, coarsely mash the raspberries so that are like a rough jam. Strain to get rid of some of the excess liquid, then put 1 tablespoon crushed raspberries into the middle of each cake.
Bake for 25 minutes, until edges are golden brown. Remove from oven and let cool, then use a thin knife to run around the edges and gently pull up on each cake to remove. Store in airtight container.