Cut a thin slice off the bottom end (not the stem end) of all 16 cocktail or cherry tomatoes, and scoop out and discard the pulp.
Drain the tomatoes, cut side down, on paper towels for 10 minutes.
Combine 1/2 pound bacon, cooked and crumbled, 1/2 cup mayonnaise, 1/3 cup minced green onions and 3 Tablespoons minced romaine lettuce in a bowl. Stir gently to mix well.
Spoon this mixture evenly into the tomatoes.
Refrigerate, covered, for about an hour, but not overnight. Then serve.
Video
Notes
Be sure to get the larger size cherry tomatoes or you'll have a very difficult time stuffing these. They are sometimes called cocktail tomatoes.
Also, I think regular iceberg lettuce would work fine in this recipe.
You can use store-bought bacon pieces if you prefer.
These are not an appetizer that can be made the evening before.