Preheat oven to 400°. Cut tomatoes into 1/4-inch slices, and place on a paper towel-lined wire rack. Sprinkle tomatoes with salt. Let stand 20 minutes. Pat dry with paper towels.
Unfold 1 puff pastry sheet on a lightly floured baking sheet. Arrange tomato slices in a single layer on pastry. Stir together cheese and next 3 ingredients in a small bowl. Sprinkle cheese mixture over tomatoes.
Preheat grill to 350° to 400° (medium-high) heat. Turn 1 side of grill off; leave other side lit. Transfer tart from baking sheet to unlit side of grill, and grill, covered with grill lid, 20 to 22 minutes or until pastry is puffed and golden brown.