In a medium skillet over medium-high heat, melt 1 tablespoon of the butter. Add the Canadian bacon and cook until golden on both sides, about 6 minutes total, flipping halfway through. Set aside.
Fill a large, nonstick skillet with 1 inch of water. Add 1 teaspoon salt and bring to a simmer over medium heat. Crack 1 egg at a time into a small ramekin, then gently pour it into the simmering water without allowing the eggs to touch. Remove the pan from the heat, cover, and let the eggs poach undisturbed for 5 minutes. Using a slotted spoon, transfer the eggs to a shallow bowl and reserve.
Make the hollandaise sauce: combine the egg yolks, lemon juice, and 1/2 teaspoon salt in a blender, pulse a few times to combine, then, with the blender running, slowly add the melted butter and blend until smooth. Blend in the 1 tablespoon hot water, then season to taste with cayenne pepper and salt.
Toast the bread slices and butter, using the remaining 1 tablespoon butter.
To serve, divide the toasted, buttered bread between 4 plates. Top each bread slice with a tomato slice, a slice of Canadian bacon, and a poached egg. Pour some of the hollandaise sauce over the egg, garnish with paprika and chives, and serve immediately.