Start by cooking your bacon in a skillet until it's crispy. Once done, place it on a paper towel-lined plate to drain any excess grease. While the bacon is cooking, you can gather and prepare your other ingredients, like dicing the sun-dried tomatoes.
Lay your two slices of sourdough bread on a cutting board. Spread the pesto sauce evenly over one side of each slice. On one slice, layer the thinly sliced turkey, followed by the crispy bacon, provolone cheese, and diced sun-dried tomatoes.
Place the second slice of bread, pesto-side down, on top to close the sandwich. Spread one tablespoon of the softened butter on the top surface of the sandwich. Carefully place the sandwich butter-side down onto a preheated skillet or griddle over medium heat.
While the first side is grilling, spread the remaining tablespoon of butter on the new top side. Cook for about 4-5 minutes per side, until the bread is golden brown and the cheese is beautifully melted. For an extra melty center, you can cover the skillet with a lid while it cooks.