Sift together all of the dry ingredients. Whisk in the soda water, a little at a time, until the right consistency is achieved. The batter should coat the back of a spoon, but some excess batter should run off the spoon. Allow to rest in the refrigerator at least 1 hour before use.
Goat Cheese Filling:
Combine all of the ingredients and mix well. Shape the mixture into 1 tablespoon balls. Make sure the squash blossoms are well cleaned. Open the flowers and insert 1 goat cheese ball in each flower. Gently press the filling into the base of the flower. Cover with the petals and pinch the top to seal. Refrigerate for 30 minutes.
Preheat a fryer or a deep pot halfway filled with peanut oil to 375 degrees F.
Hold the squash blossoms by the stem. Dip each into the tempura batter, making sure to coat completely. Let any excess batter drip off. Place the blossom in the oil and fry until golden brown, about 1 to 2 minutes, turning often to brown evenly. Remove to a paper towel lined plate.
Place some of the Tomato Sauce on the bottom of a plate. Top with 2 squash blossoms and garnish with Fried Basil leaves.
Heat a large saute 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. Add 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 mixture is of sauce consistency, about 15 minutes. Add the thyme, basil, and remaining olive oil and mix well.
Fried Basil Leaves:
Heat about 1/2-inch of the oil in a steep-sided saute pan to 350 degrees F. Or heat a deep fryer to 350 degrees F.
Pat the basil leaves dry to remove any surface water. Carefully drop the basil leaves in the hot oil. The oil will spit and splatter as the moisture in the leaves fries. Fry for 10 seconds or just until the leaves start to become translucent. Remove with a slotted spoon to a paper towel lined plate.