Slice the tomatoes into 1.5-2cm (1/2-3/4") slices. Slice the halloumi into 1/2-1cm-thick slices. Oil the tomato and halloumi slices, reserving some of the oil. Grill at medium-high heat on either side for several minutes per side. Place tomatoes, top with the halloumi. Drizzle with reserved olive oil. Sprinkle with cilantro and Maldon salt and serve.