Heat oven to 425°F with a bare rimmed sheet on middle rack. Cover potatoes with cold water by 1 inch; add cooking salt. Simmer 7 to 8 minutes after bubbling starts until outsides soften but centers slightly resist.
Drain well; steam-dry 3 minutes. Gently toss with oil, seasoning salt, oregano, garlic powder, and pepper.
Carefully space potatoes cut-side down on hot pan. Roast undisturbed 25 minutes.
Turn; roast 5 to 10 minutes more until fully tender and deeply golden underneath.
Lightly toss in a bowl with lemon zest and juice; serve immediately while crisp.