Start by spreading your sour cream mixed with salt across the bottom of a 9x13 baking dish. Mix it together with a fork first so the salt gets evenly distributed. This becomes your creamy base layer for the entire 7 layer dip crowd favorite.
Layer your mashed avocados on top, pressing gently so you don't mix it with the sour cream below. Drizzle the lime juice over the avocado right away to stop it from browning. I learned this the hard way after making this for my sister's birthday party.
Spread your drained black beans as the third layer across the top. Don't skip rinsing them—I did once and regretted it immediately. The starchy water makes everything look gray and soggy.
Pour your salsa evenly over the beans, keeping it at medium thickness so layers stay visible. My 6-year-old eats three helpings just for this layer, honestly. Too much salsa and you lose the beautiful color separation.
Sprinkle your shredded cheddar cheese across the entire surface in an even layer. Don't go crazy here—you want people to see those gorgeous layers underneath. About 1 cup gives you good coverage without overdoing it.
Top with diced tomatoes, cilantro, and olives in whatever pattern you like. Drizzle the olive oil over everything and finish with a tiny pinch more salt. This final step is where the 7 layer dip crowd magic actually happens.