Brown the sausage: Heat a large skillet over medium heat and add the ground sausage. Break it into small crumbles with a spatula and cook until no pink remains, about 8 minutes.

Drain excess fat: Tilt the skillet and spoon or drain off any excess grease so the dip doesn't turn oily.

Add tomatoes and beans: Stir in the Rotel tomatoes, black beans, and taco seasoning. Let the mixture simmer for 2-3 minutes until fragrant.

Lower the heat: Reduce the heat to low so the cheese melts smoothly without breaking or turning oily.

Melt in cream cheese: Add the cream cheese in small cubes, stirring constantly until each piece fully melts into the mixture, about 3 minutes.

Melt in Velveeta: Add the Velveeta cubes a handful at a time, stirring until smooth before adding more, about 5 minutes total.

Fold in cheddar: Stir in the shredded cheddar gradually until the dip is glossy, thick, and coats the back of a spoon evenly.

Check the texture: The dip is done when no lumps of cheese remain and small bubbles rise slowly at the surface.

Garnish and serve: Transfer the dip to a serving bowl and top with sliced green onions. Serve warm with tortilla chips or sliced vegetables.