For the potatoes: In a large bowl of cold water, add the potato slices and rest at room temperature, draining, rinsing and changing the water halfway through, for 30 minutes.
For the loaf: Preheat the oven to 350 degrees F. Spray the inside bottom and sides of a nonstick bundt pan with cooking spray.
In a large bowl, add the breadcrumbs, onion, pesto, ketchup, 2 teaspoons salt and plenty of black pepper. Stir to combine and whisk in the eggs. Add the meatloaf blend and gently mix to distribute the ingredients. Press the meatloaf into the prepared bundt pan and bake for 30 minutes.
Line a baking sheet with aluminum foil. Remove the bundt pan and, using a medium bowl or liquid measure cup, gently tilt the pan and drain out the juices, reserving 1/2 cup. Place the foil-lined baking sheet on top of the bundt and, holding them together, flip them to unmold the loaf onto the baking sheet. Turn the oven up to 375 degrees F.
Drain, rinse and dry the potatoes on a paper towel-lined plate. Wipe out the bowl and place the potatoes back in along with the melted butter, a pinch of salt and a few grinds of pepper. Gently mix to coat. Begin to layer the curved top of the loaf with the potato slices, overlapping them slightly around the loaf, covering the top and about one-third of the way down the side of the loaf all around. Return to the oven and continue to bake until the potatoes begin to curl and become slightly golden on the edges, about 30 minutes more. Rest 10 minutes, then transfer to a serving dish.
For the glaze: In a medium saucepot on medium-high heat, add the 1/2 cup pan drippings, the ketchup, a pinch of salt and a few grinds of pepper. Bring to a simmer, lower the heat to medium and cook until the sauce thickens and reduces, 8 to 10 minutes. Remove from the heat, add the hot sauce and stir in the parsley. Pour over the loaf and serve.