Bacon: Adjust oven racks to upper middle and lower middle positions and preheat oven to 400°F. Line 2 rimmed baking sheets with foil. Arrange 8 bacon strips in single layer on each sheet. Bake until crisp, 16 to 18 minutes, alternating sheets’ positions and turning bacon strips with tongs halfway through baking.
Transfer sheets to cooling racks and transfer bacon to large plate. When cool enough to handle, discard rendered fat and foil.
Toast all slices of bread in toaster just to get golden brown.
Transfer bread to cutting board. Spread 4 slices with mayonnaise. Add cheese, bacon, green tomato, beefsteak tomato, green tomato, and basil.
Top remaining 4 slices of bread with tomato jelly and place on top of the sandwich to complete. Slice on the diagonal and serve.
Turkey Bacon or Roasted Turkey Breast are a great substitution.