Mediterranean Burger with Creamy Feta-Curry Dressing

large vine-ripened tomatoes, sliced into 8 rounds

seasoned rice vinegar

ground chuck

ground lamb

ground pork

container (5.3 oz) nonfat, plain Greek yogurt

mayonnaise

crumbled feta cheese

freshly chopped mint

fresh lemon juice

curry powder

finely chopped garlic

coarse ground black pepper

large red onion, sliced into rings

poppy seed Kaiser rolls or other good quality buns