Place the bacon in a small skillet; heat over medium heat until beginning to sizzle. Reduce the heat to medium low; cook until crisp and golden brown, about 8 minutes. With a slotted spoon, remove the bacon to a paper towel-lined plate, leaving the fat in the pan.
Add the breadcrumbs to the hot bacon fat; cook, stirring often, until lightly toasted and crunchy, about 3 minutes. Remove the breadcrumbs to a separate paper towel-lined plate, spread evenly, and then sprinkle with the Parmesan to melt slightly.
With a rubber spatula, mix together the mayonnaise, lemon juice and salt in a bowl. Add the shredded romaine; toss well to coat.
Cut a small amount off the bottom of each tomato to create a flat surface to sit on. Then cut off the tops as well. Run a small knife around the inside of the tomatoes to loosen the flesh. Using a 1/2-teaspoon measuring spoon, scoop out and discard the insides of each tomato.
Divide the bacon among the tomatoes, pushing it down slightly. Top with some of the romaine, followed by the bacon-parmesan breadcrumbs. Serve at room temperature.