In a medium bowl combine 2 cups flour, 1/2 tsp instant yeast, 1/2 tsp salt and 1/4 tsp sugar. Stir to blend. Add 1/2 cup warm water and 1 tbsp olive oil. Mix until a shaggy dough forms, then knead on a lightly floured surface for 5–7 minutes until smooth and elastic. Form into a ball, place in a lightly oiled bowl, cover with plastic wrap or a towel and let rest in a warm place for 30–45 minutes until roughly doubled.

When ready to bake, preheat the oven to 500°F (260°C). If you have a pizza stone, place it in the oven to heat. If not, use a rimless baking sheet or a heavy baking sheet turned upside down and heat it in the oven.

Punch down the dough and divide into 2 portions for thin individual tartes (or keep whole for one large). On a lightly floured surface roll or stretch each portion as thin as possible into a rough rectangle or oval about 10–12 inches long. Transfer to a piece of parchment for easy transfer to the hot stone or sheet.

Topping Base

Prepare the fromage blanc spread

While dough rests, combine 1 cup fromage blanc with 2 tbsp sour cream (if using) in a bowl to reach a spreadable consistency. Stir in 1/2 tsp salt, 1/4 tsp freshly ground black pepper and 1/8 tsp grated nutmeg. Taste and adjust seasoning — the base should be tangy but not overly salty because the lardons and Gruyère will add salt.

Toppings

Cook lardons and soften onions

Heat 1 tbsp butter (or oil) in a skillet over medium heat. Add the thinly sliced onion and sauté for 3–4 minutes until beginning to soften. Add 6 oz lardons (or diced bacon) and continue to cook 5–6 minutes, stirring occasionally, until the bacon is cooked through and onions are translucent and lightly golden. Remove from heat and drain any excess fat on paper towels if very greasy. Set aside.

Assemble the tarte

Spread a thin, even layer of the fromage blanc mixture over each rolled dough, leaving a 1/4 inch border. Distribute the cooked lardons and onions evenly over the base. Sprinkle 1 cup grated Gruyère evenly on top (divide between two small tartes if making two).

Slide the parchment with the assembled tarte onto the preheated stone or hot baking sheet. Bake at 500°F (260°C) for 8–12 minutes, rotating once if necessary, until the crust is blistered and golden at the edges and the cheese is bubbling and starting to brown. For a very thin crust expect closer to 8–10 minutes; a thicker crust may need the full time.

If you prefer a slightly crisper top, switch the oven to broil for the last 1 minute — watch closely to prevent burning.

Finishing

Remove the tarte from the oven and transfer to a cutting board. Drizzle with 1 tsp extra virgin olive oil and sprinkle a little freshly ground black pepper. Scatter 1 tbsp chopped fresh chives or parsley over the top if using.

Slice into wedges or rectangles and serve immediately while hot and crisp.