Roll out the pizza dough and place on a pizza baking pan, or a pizza stone.
Spread pizza sauce mixture over the crust. Top with feta cheese. Top with the lamb evenly over the entire pizza. Top with red onions and olives and sprinkle the oregano over the entire pizza.
Bake for 10 to 15 minutes or until crust is golden brown.
Tzatziki sauce
Put the cucumber in a strainer set over a bowl. Sprinkle with 1/2 teaspoon salt and drain for 1 hour. Put the yogurt in another strainer set over a bowl and drain for 1 hour. Combine the cucumber and yogurt in a bowl with the remaining ingredients and stir well. Cover and chill for at least 1 hour before serving.