Preheat the oven to 375 degrees, and set a rack in the lower third of the oven. Lightly spray a round 9-inch pie dish, or a 1 quart/1 liter baking dish, with vegetable oil, or grease with butter.

Whisk the eggs together in a medium bowl. Add ½ cup sugar and lemon zest, and mix. Fold in the ricotta. 

Pour the mixture into the baking dish, and bake in the oven for 15 minutes.

Carefully remove the dish from the oven, and evenly scatter the berries over the batter. Sprinkle with 1 tablespoon sugar and return to the oven.

Bake until the middle is completely set, the edges start to brown, and the soufflé is puffed, about 20 minutes.

Serve warm, at room temperature, or chilled. Store in the fridge, covered, for up to 3 days. Do not freeze.