Make the pesto: Add basil, garlic, parmesan, toasted pine nuts, and a pinch of salt to a food processor. Pulse a few times to roughly combine. With the processor running slowly drizzle in olive oil until the pesto reaches your desired consistency — add more oil for a smoother texture, less for something thicker and more intense. Taste and adjust salt.
Prep the tomatoes: Slice the heirloom tomatoes thickly and season with salt and pepper. Set aside for a few minutes to draw out the juices.
Spread the pesto: Spread a generous layer of pesto on both cut sides of the ciabatta — don't be shy here, this is the flavor base of the whole sandwich. Layer the fillings: On the bottom half layer the prosciutto slices. Add a handful of arugula. Break open the burrata and spread it over the arugula so it covers the bread evenly — let the creamy center spill out. Layer on the heirloom tomato slices.
Finish: Drizzle generously with olive oil and balsamic glaze. Season with a little more salt and pepper.
Close and serve: Place the top half of the ciabatta on and press gently. Slice in half and serve immediately.