In a blender combine flour, milk, eggs, Stevia In The Raw®, lemon zest, vanilla, and salt. Blend until smooth, then let rest for 30 minutes.
Preheat oven to 425℉. Place a 9” cast iron skillet in oven to preheat.
When ready to bake, add butter to hot skillet, swirling to coat pan. Pour in batter, quickly sprinkle blueberries over the top, and bake until puffed and golden, 15-20 minutes.