Place 2 of the coarsely chopped avocados in a large mixing bowl and mash them it the back of spoon or a potato masher. Continue mashing until the avocado slices for thick, smooth and watery paste.
Add in one large seeded and finely diced Serrano chile and mix it with the avocado paste.
Sprinkle the mixture with the ¼ cup of slice onion and 1/8 cup of coarsely chopped cilantro leaves.
Now fold in ¼ cup of sour cream and then drizzle 1 tablespoon of freshly extracted lemon over the mixture.
Use a large spoon to toss the ingredients. Now cover this bowl and set aside.
Dice the remaining 2 avocados into half-inch cubes and fold them into the mixture in the bowl.
Top the mashed avocado mixture with seeded tomato slices and dust with some salt and ground black pepper. Flippantly toss the mixture to merge ingredients.
Arrange some warm flour tortillas around a large platter and spoon the Simple Guacamole in the center.
Garnish your Simple Guacamole with some roughly chopped parsley leaves and serve immediately.