Heat a large cast-iron skillet over high heat until very hot and brush lightly with vegetable oil. In a bowl, toss the okra with 1 Tbs. of the oil and season with 1/4 tsp. salt. Cook the okra in the pan in two batches, turning once, until charred and tender, 3 to 4 minutes per batch depending on the size and freshness of your okra. Reserve in a bowl so you can reuse the cast-iron skillet.
Add 1 Tbs. of the oil to the corn and season with 1/4 tsp. of the salt. Add the corn to the skillet and cook over high heat, stirring occasionally, until lightly charred in spots, about 3 minutes. Reserve the corn in a bowl, separate from the okra.
Bring a large saucepan of water to a boil and fill a bowl with ice water. Score the tomato bottoms with an X. Add the tomatoes to the boiling water and blanch for 10 seconds to loosen their skins. Transfer the tomatoes to the ice water to cool. Core and peel the tomatoes, and halve them crosswise. Working over a sieve set in a bowl, tease out the seeds with your fingers. Press on the seeds to extract the juice, then discard them. Chop the tomatoes and reserve them in the bowl of their juice.
Pour the remaining tablespoon oil into the skillet over medium-high heat, and when it shimmers, add the bacon. Sauté the bacon until it just begins to brown, about 4 minutes, then add the onion and 1/2 tsp. salt. Stir continuously for about 2 minutes, allowing the onion to release some moisture, but not letting it brown. Add the garlic and cook for about a minute to let its flavor bloom (do not brown the garlic). Then add the tomatoes, and stir to combine. Cover the pot, reduce the heat to medium, and cook for about 4 minutes until the tomatoes have mostly collapsed.
Add the corn, stir to combine, and cook for 3 more minutes. Add the okra, stir, and cook just until the okra is heated through, about 2 minutes. Season to taste with the vinegar (which you may or may not need, depending upon the acidity of the tomatoes), salt, and black pepper; serve.