Slice the sausage into rounds or bite-sized pieces.

Heat the butter in a pan over medium heat.

Add the sausage slices and cook until browned and slightly crispy on both sides. If using optional onion, add it now and cook until softened.

While the sausage cooks, halve the avocado, remove the pit, and slice or dice the flesh.

Remove the pan from the heat. Add the avocado pieces to the warm pan with the sausage.

Gently stir everything together in the residual heat of the pan, letting the avocado soften slightly and coat in the buttery sausage juices.

Season with a pinch of salt and pepper.

If using, toast the optional bread and pile the sausage and avocado mix on top. Serve immediately, adding a squeeze of optional lemon if desired.