Put the cornmeal, flour, 1 teaspoon of the salt, and homemade baking powder in a mixing bowl and stir well with a whisk to blend.
In separate bowl, whisk together the egg and water and stir into the dry ingredients, mixing only until moistened.
Sprinkle the remaining salt and freshly ground pepper over the onion and sliced okra and toss lightly.
Fold the vegetables into the batter.
Pour 1 inch of oil into a heavy skillet and heat to 340-350 degrees F.
Spoon the okra batter by heaping tablespoons into the hot oil.
Fry until golden brown on one side, then carefully turn and continue until both sides are browned and the fritters are cooked through.
Remove from the skillet and drain well before serving.
For homemade baking powder: Sift the ingredients together 3 times and transfer to a clean, tight-sealing jar.
Store at room temperature away from sunlight for up to 6 weeks.