Preheat the oven to 220°C. Whisk together the first 3 ingredients. In a large nonstick pan, heat 1 tablespoon butter over medium heat. Add egg mixture; cook and stir until eggs are thickened and no liquid egg remains. Remove from heat.
Place 2 tortillas on a baking sheet. Top with eggs, salsa, cheese and remaining tortillas. Melt remaining butter; brush over tops.
Bake until golden brown and cheese is melted, 10-12 minutes. If desired, serve with sour cream and additional salsa and herbs.