Shred potatoes and onion using a food processor or box grater.

Place shredded potatoes and onion in a large bowl.

Stir in lemon juice, tossing to combine.

Place potato mixture in a colander and drain for 15 minutes, pressing down occasionally to remove excess moisture.

Squeeze out any remaining liquid from the potato mixture using your hands.

In a large bowl, combine the potato mixture with flour, thyme, salt, and pepper.

Add egg and egg yolk, and stir well to combine.

Preheat oven to 225°F (107°C).

Line a baking sheet with paper towels.

Heat canola and olive oils in a 10-inch skillet over medium-high heat until it reaches 350°F (175°C).

Working in batches of 4, carefully drop 1/4-cupfuls of potato mixture into the hot oil.

Gently flatten each portion with a spatula into 2 1/2-inch circles.

Cook for 3 minutes on each side, or until browned and crisp.

Remove latkes with a slotted spatula, allowing excess oil to drain back into the pan.

Place latkes in a single layer on the prepared baking sheet.

Keep warm in the preheated oven.

Repeat the frying process with the remaining potato mixture, ensuring the oil temperature remains at 350°F (175°C).

Serve warm with sour cream and applesauce, if desired.