Combine marinade ingredients in a small bowl and mix well.
Coat tempeh slices in sauce, ensuring each slice is submerged. Allow them to soak for at least half an hour, but preferably an hour or longer for optimal flavor.
Grease skillet, if necessary and cook tempeh “bacon” over medium-high heat.
Toast chosen bread. While it’s toasting, mash avocado, adding lemon juice to preserve colour if desired.
Top toast with mashed avocado, then finish with slices of tempeh bacon.