Toast. Toast the English muffin halves. You can use a regular toaster. For extra flavor, you could toast them in a pan over medium-high heat with a bit of butter until lightly golden.
Eggs. Whisk the eggs with a pinch of salt. Cook the scrambled eggs to your preference. For sandwiches like this one, I like making the scrambled eggs in big curds and fluffy, almost like mini omelets. To do that, to a frying pan over medium-high heat, add the butter. When the butter is melted, add the whisked eggs. As soon as they start to set on the edges, push them to the center using a rubber spatula and gently fold over. Make sure they don’t burn on the bottom.
Assemble. Assemble the sandwiches. Spread pesto on both sides of the English muffin (about 1/4 tbsp each side). On the bottom half, add the mozzarella slices and season with a pinch of salt. Top the mozzarella slices with the scrambled eggs/mini omelets. On the top one, add the tomato slices (already seasoned with a pinch of salt). Put the top half of the English muffin over the eggs. Serve immediately before the eggs get cold.