Whisk egg yolks and lemon juice in a heatproof bowl. Place over gently simmering water and whisk continuously. Slowly drizzle in melted butter while whisking until sauce thickens. Season with salt, black pepper, and cayenne, then keep warm. Toast English muffins until golden. Warm Canadian bacon in a skillet for 1–2 minutes per side. Bring a pot of water to a gentle simmer and add vinegar. Crack eggs into small bowls and carefully slide into simmering water. Cook for 3–4 minutes until whites are set and yolks remain soft. Remove with a slotted spoon. Assemble by placing Canadian bacon on each muffin half, topping with a poached egg, and spooning hollandaise over the top. Serve immediately.