In a mixing bowl, whisk chickpea flour and salt together.
Gradually add water while whisking to form a smooth, lump-free batter.
Stir in ¼ cup olive oil and let the batter rest for 1 hour at room temperature.
Preheat the oven to 450°F (230°C) and place a 10-inch cast-iron skillet or baking dish inside to heat.
Once the skillet is hot, carefully remove it from the oven and coat the bottom with a drizzle of olive oil.
Pour the batter into the skillet, spreading it evenly. Sprinkle fresh rosemary on top if desired.
Bake for 20-25 minutes or until the farinata is golden and crisp around the edges.
Let cool slightly before slicing and serving. Serve with sea salt flakes and freshly ground black pepper if desired.
