Preheat the oven to 425 degrees and bring a pot of lightly salted water to boil. Drop the potatoes and 1/3 of your lemon juice into the water and boil until just fork tender, about 10 minutes.
Toss (gently!!) the drained potatoes with the olive oil, remaining lemon juice, lemon zest, cumin, sumac, salt, pepper and garlic powder. Lay out on your baking sheet and bake until golden and crispy, about 15-25 minutes (depending on your oven and preference).
Crumble about 2 tbsp feta on top of each serving of potatoes when you serve. Done!