Stir the flour, yeast, and salt together. Add the warm water and olive oil and knead for 6 to 8 minutes until smooth.
Cover the dough and let it rest in a warm place for 30 minutes. Divide it into 6 balls.
Mix the topping:
Pulse the onion, bell pepper, tomatoes, parsley, garlic, tomato paste, cumin, pepper, and olive oil in a food processor until finely minced but not completely smooth.
Mix the vegetable mixture with the ground beef and season with salt. Keep it chilled while the oven heats.
Shape and bake:
Heat the oven to 475 F (245 C) with baking sheets inside if possible.
Roll one dough ball into a very thin oval. Spread a thin, even layer of beef topping almost to the edge.
Transfer to parchment and bake for 7 to 9 minutes until the edges are browned and the topping is cooked. Repeat with the remaining dough and topping.
Serve:
Top each hot lahmacun with parsley, red onion, and a squeeze of lemon.
Roll or fold while warm and serve immediately.
Notes
A hot baking surface helps the thin dough crisp quickly.
The topping should be finely minced so it cooks in the short bake time.
Freeze cooled baked lahmacun between sheets of parchment for up to 2 months.