Preheat the oven to 375ºF.
Separate the onion slices into rings. In a large bowl, stir together the buttermilk, 1/2 teaspoon of the salt, and 1/4 teaspoon of the pepper. Immerse the onion rings in the buttermilk mixture.
In another large bowl, combine the flour, cornmeal, remaining 1/2 teaspoon salt, and remaining 1/4 teaspoon pepper. Pour the cornmeal mixture onto a large platter.
Coat 2 baking sheets with the canola oil, using 2 tablespoons for each. Place the sheets in the oven and heat for 5 to 7 minutes. The heated oil will help give the onion rings a crispy texture.
With tongs or fingers, remove the onion rings from the buttermilk mixture and put them in the cornmeal mixture. Turn the rings in the cornmeal mixture to coat them evenly. Remove the baking sheets from the oven and arrange the rings on the heated sheets in a single layer. Bake until the undersides of the rings have started to brown, about 10 minutes. Remove the sheets from the oven and turn over the rings. Return to the oven and bake for another 5 minutes or until the bottoms are browned. Serve hot.
Recipe courtesy of At the Farmers’ Market with Kids: Recipes and Projects for Little Hands by Leslie Jonath & Ethel Brennan/Chronicle Books, 2012.