First, cut the tempeh in half lengthwise, then cut into 12 *triangles. There is no need to steam the tempeh, unless you want to; see notes.
Make the Chimichurri sauce using a food processor and add the entire batch to a small bowl. Then add 1/2 water and stir to combine.
To an 8x8 baking dish (or a shallow dish), add 1/2 the sauce. Then add the tempeh pieces. Finally, add the remaining sauce evenly so it completely covers the tempeh. If the sauce does not cover the tempeh completely, you can add a bit more water to ensure all of the tempeh will be marinated. Let marinate in the fridge overnight for best results (or at least a few hours). The longer you marinate, the more infused the flavor will be.
When ready to bake, line a baking sheet with parchment paper. Then transfer the tempeh pieces to the baking sheet. Some of the chimichurri sauce is ok to be baked, but just make sure there is not additional liquid on the baking sheet. Bake the tempeh at 400 F for 22-28 minutes or until golden brown.
Remove from oven and transfer the tempeh pieces to a serving dish. Add a tablespoon or two of chimichurri sauce on top of each piece of tempeh. Serve. Store in an airtight container in the fridge for up to 3 days. Best served fresh.