Remove pan from heat, remove garlic and marjoram from pan with slotted spoon and transfer to a paper towel lined plate to drain. Season lightly with salt. Reserve oil from pan, transferring it to a small bowl.
Toss the drained tomatoes with 2 tablespoons of the reserved oil and season with salt.
Transfer tomatoes to a foil lined cookie sheet and place under the broiler until skins begin to char and tomatoes begin to shrivel, about 5 minutes. Remove tomatoes from oven and allow to cool.
Next, transfer mascarpone to a medium bowl, season with salt. Take half the fried garlic and marjoram mixture, roughly chop, then add to the bowl of seasoned mascarpone. Mix well with a wooden spoon. Set aside.
Brush the 6 pieces of ciabatta, cut side up, with remaining garlic and marjoram oil, place on a cookie sheet, then place under the broiler to quickly and lightly toast, 3 minutes or so. Stay with the bread, rotating as necessary to make sure it toasts evenly. Remove toasted bread from oven, let cook a minute or so and begin assembling the tartines.
Divide the mascarpone mixture among the 6 toasts, spreading it evenly with a spatula or a butter knife. Gently arrange the charred cherry tomatoes on each toast.
Garnish each toast with some of the remaining fried garlic and marjoram, a drizzle of any remaining oil leftover, and freshly ground black pepper