Preheat the oven to 390°F (200°C). Grease a 9x13-inch baking tray with a bit of oil and place it in the preheated oven for 7–8 minutes while you prepare the batter.
Mix dry ingredients: In a large bowl, whisk together the flour and baking powder.
Combine wet ingredients: Add the grapeseed oil to the dry ingredients and mix. Gradually stir in the carbonated water, followed by the sugar and lemon juice. Mix until the batter is smooth and well combined.
Assemble: Carefully remove the baking tray from the oven. (MAKE SURE YOU LEAVE THE BATTER FOR AT LEAST 10 MINUTES TO HELP MAKE IT FLUFFIER BEFORE POURING IT INTO THE TRAY & REWHISK BEFORE POURING OUT.) Pour the batter into the hot tray and gently spread it evenly. Sprinkle the fresh raspberries on top.
Bake: Place the tray back in the oven and bake at 390°F for 5 minutes. Then reduce the temperature to 375°F (190°C) and bake for an additional 25–30 minutes, or until the edges are golden and a toothpick inserted into the center comes out clean.
Serve: Let the dessert cool slightly before slicing. Enjoy warm or at room temperature!
