Summertime Tomato Salad

½ cup vegetable oil

¼ cup white vinegar

½ teaspoon white sugar

½ teaspoon ground black pepper

1 teaspoon Dijon mustard

2 teaspoons seasoned salt

3 tomatoes, diced

2 onions, diced

Whisk together the vegetable oil, vinegar, sugar, pepper, mustard, and seasoned salt in a bowl; add the tomato and onion to the bowl and toss to coat; cover and refrigerate overnight.