Position a rack in the center of the oven and preheat to 375ºF (190ºC).
Shuck the corn and remove the silk. Holding an ear in a shallow bowl, use a sharp paring knife to cut the kernels off of the corn. Reverse your knife and scrape any remaining good stuff off of the cob as well. Repeat with the other ear, discarding the cobs. Prepare the other vegetables and the cheeses and have them at the ready.
Place the butter in a 10" oven-proof skillet and set the skillet in the oven to melt the butter, about 5 minutes.
In a large bowl, whisk together the oat flour, rice flour, cornmeal, baking powder, baking soda, sugar, and salt. Whisk well to eradicate lumps. Add the eggs and kefir, and stir until just combined.
Remove the pan from the oven, swirl to coat the sides with butter, then pour the melted butter into the batter along with the corn and grated cheese, stirring quickly and gently to combine.
Scrape the batter into the buttery, hot pan, and spread evenly. Top with the tomatoes, peppers, feta, and onions. Bake the cornbread until golden on top, and a toothpick inserted into the center comes out clean, 35-45 minutes. (The cooking time will vary depending on the moisture in your vegetables, the thickness of the kefir, the temperature of the oven, the material of your baking pan, etc., so just keep cooking it until it passes the toothpick test.)
Let the cornbread cool for at least 1 hour; the bread is still cooking from residual heat. Cut into wedges and serve. Extras can be kept airtight at room temperature for up to a few days.
Notes
Adapted from my Gluten-Free Buttermilk Skillet Cornbread.Feel free to use whatever vegetables you like here. Thinly sliced sweet peppers could easily stand in for the padrons, or add chopped roasted green chiles to the batter if you like a bit of a kick.I used two sheep milk cheeses from Garden Variety; Black-Eyed Susan, a fairly firm melting cheese similar in texture to an aged cheddar or fresh pecorino, and a salty and also fairly firm feta.I like to bake this in my 10-inch round cast iron skillet, but it should also work in a 9-inch round pan or skillet, or a 9-inch square pan.If you or your guests are severely allergic to gluten, be sure to seek out ingredients (especially oat flour) that are certified gluten-free. If you can't find sweet white rice flour (mochiko), substitute regular white rice flour and add 1/4 teaspoon xanthan gum to help the bread hold together. If gluten isn't an issue, give this a go with all-purpose and whole wheat flours in place of the rice and oat.All ounce measurements are by weight.Nutritional values are based on one of eight servings.