Gather three bowls. In one bowl whisk the buttermilk and eggs together. In another, add the flour. In the third, mix the breadcrumbs, cornstarch, and salt.
Take each slice of tomato and gently dip it into the flour, then the egg mix. Repeat this process once more, then dip the tomato into the breadcrumb mix.
Heat the oil in a heavy-based pot to 375°F. Gently add the crumbed tomato into the oil and fry on each side until golden brown. Place onto a paper towel or a metal rack to drain.