Slice your 2 large russet potatoes lengthwise into fries about 1/4 inch thick. Don't overthink the sizing—just aim for consistency so they cook evenly. I use a knife, but honestly, a mandoline works if you've got one and you're careful with your fingers.

Soak the sliced potatoes in the 1/2 cup cold water mixed with 1 tsp lemon juice for 10 minutes. This step removes excess starch and keeps them from browning too fast. I learned this the hard way—skip it and they'll turn grayish instead of golden.

Drain the potatoes completely in a colander and pat them bone-dry with paper towels. Seriously, don't skip the drying part or they'll steam instead of crisp up. I mean it—use about 4-5 paper towels and really press the moisture out.

In a bowl, mix together 1 tbsp cornstarch, 1/2 tsp baking soda, 1 tsp salt, 1/2 tsp black pepper, 1/2 tsp smoked paprika, 1/4 tsp garlic powder, 1 tsp dried rosemary, and 1/4 tsp onion powder. This is your seasoning base, and you can adjust it to your taste. Some people add cayenne for heat, but I stick with this blend.

Toss the dried potatoes with the seasoning mixture until every piece is coated. Work quickly so the potatoes don't reabsorb moisture. The coating should look like a light powder on each fry.

Arrange the fries in a single layer inside your air fryer basket without crowding. Overcrowding kills the crispiness, so work in batches if you need to. I usually fit about half the potatoes per batch depending on my fryer size.

Air fry at 400°F for 18-20 minutes, shaking the basket halfway through cooking. You'll hear it sizzle once it gets going—that's a good sign. Pull them out when they're golden brown and crispy on the edges, then let them rest for 2 minutes before serving.