In a medium bowl, sift together the dry ingredients; whisk together both flours, baking powder, 1 teaspoon salt.
Gradually add the sparkling water, adding more as necessary so that batter is a thin consistency. The batter should coat the back of a spoon, but some excess should runoff. Allow it to rest in the refrigerator at least 30 minutes before use.
Heirloom Tomato Sauce
Heat a large sauté pan over medium-high heat. When the pan is hot, add 3 tablespoons of the olive oil and heat.
Add the onion, garlic, and chili flakes and cook for 1 minute. Insert the tomatoes and season with salt and pepper. Add the sugar and stir to combine. Lower the heat and cook until the tomatoes start to disintegrate, and the mixture is of a sauce-like consistency, about 15 minutes.
Add the thyme, basil, and remaining olive oil (1-2 tablespoons) and mix well. Allow it to cool to room temperature, reserve.
Ricotta Filling
While the batter is chilling, prepare the squash blossoms.
Carefully separate the flower petals without breaking them and remove the pistil in the center. Combine the cheese, basil, parsley, mint, chives, thyme, lemon peel, olive oil, salt, and pepper until smooth.
Place mixture in a piping bag or small plastic bag and cut a small hole on the tip. Carefully add about 1-2 teaspoons of the cheese mixture to each blossom and twist the top of the flower tight.
Frying the Squash Blossoms
Fill a deep pot 2-inches high with vegetable oil. Heat over medium-high heat until it reaches 375°F on a thermometer.
Hold the squash blossoms by the stem. Dip each into the batter, making sure to coat thoroughly. Let any excess batter drip off. Place the blossom in the oil and fry until golden brown and crispy, about 1 to 2 minutes, often turning to brown evenly. Transfer to a paper towel-lined tray. Season with salt and pepper.
Serve and enjoy the fried blossoms immediately and serve with Heirloom tomato sauce.