Preheat the oven to 400°F. Line a baking sheet with parchment and set aside.
Make the sour cream drizzle by blending all the ingredients together. Run the blender’s motor on high until you have a smooth and fluid dressing, adding more water by the tablespoon, if necessary. Check the drizzle for seasoning, adjust if necessary, and set aside.
Make the potatoes. Place the potatoes in a medium saucepan and cover with cold water. Place the saucepan over medium-high heat. Bring the potatoes to a boil and then simmer until tender, about 15 minutes. Drain the potatoes and arrange them on the baking sheet.
Using the bottom of a glass or measuring cup, gently apply pressure onto each potato to flatten them slightly. Then, spoon about 1 teaspoon of the sun-dried tomato pesto on top of each potato and spread it around to cover each potato’s surface. Gently flip the potatoes over and spread the remaining pesto on the other side. Slide the baking sheet into the oven.
Bake the potatoes until the edges have browned, about 20 minutes, gently flipping the potatoes over at the halfway point. Serve potatoes warm with the caesar drizzle and chopped basil.