Heat the Oven - Set the rack to the center position. Heat the oven to 425°F (246°C).
Cut the Potatoes - Wash, scrub, and dry the potatoes. Place each potato between two chopsticks to prevent cutting through completely. Using a small knife, make ⅛ inch slices across the potato, stopping about ¼ inch from the bottom.
Season the Potatoes - In a medium bowl, combine the potatoes, olive oil, garlic, salt, and pepper.
Roast the Potatoes - In an 8x8-inch baking dish, evenly place the rosemary and thyme sprigs on the bottom. Place the seasoned potatoes with the cut side facing up. Add slices of lemon. Roast until tender, about 30 minutes.
Make the Lemon Sauce - In a medium bowl, whisk together apple cider vinegar, lemon juice, shallots, rosemary, thyme, salt, and pepper. Gradually drizzle olive oil into the bowl while vigorously whisking to create a thickened sauce.
To Serve - Drizzle the lemon sauce onto the warm roasted potatoes or serve on the side.
Notes
Make it Whole30: Use sea salt for kosher salt.
Storing: Store the potatoes in an airtight container in the refrigerator for up to 3 days.
Reheating: Reheat in the oven at 350ºF (177ºF) until warmed and crisp, or microwave in 30-second increments until hot.