Zaatar is a Middle Eastern spice blend made of sesame seeds, sumac and thyme. You can buy it at Mediterranean food shops (you can also substitute thyme or oregano).
Rinse the haloumi to remove excess salt, and pat dry with paper towels.
Cut the haloumi in slices about 1cm thick, and lightly dust with flour. Fry the slices in olive oil until golden brown on both sides. It should be just melting.
Sprinkle with zaatar and squeeze over a little lemon juice.