Preheat the oven to 425℉.
In a large bowl, combine the melted butter, safflower oil, Plain Unsweetened Low-Fat Kefir, sour cream, eggs, and sugar. Stir to combine.
In a separate bowl, whisk together the flour, salt, baking powder, and baking soda. Add the dry ingredients into the wet ingredients and whisk to combine.
Add the vanilla and the roasted balsamic strawberries. Stir gently to combine (the mixture will be very thick).
Coat a doughnut pan with oil or cooking spray. Fill each opening approximately 3/4 full, smoothing with a spoon.
Bake for 14-15 minutes until the tops start to brown. Remove the doughnuts from the oven and allow to cool for about 5 minutes in the pan. Next, transfer the doughnuts to a wire rack to cool completely.
Preheat the oven to 350℉.
In a small bowl, combine the strawberries, balsamic vinegar, sugar, and salt. Stir to combine. Pour onto a rimmed baking sheet. Bake for 20-30 minutes until the strawberries are soft and bubbly, stirring once while cooking.
Remove from the baking sheet and store in an airtight container in the refrigerator until ready to use.
In a medium-sized bowl, combine the Low-Fat Strawberry Kefir, powdered sugar, and vanilla extract. Whisk to combine. Once the doughnuts are completely cooled, dip each doughnut in the glaze to coat.
Store the doughnuts in the refrigerator since the glaze contains milk.