Sometimes chocolate theme weeks overlap and become akin to nested Russian dolls. In this case 100 percent cacao chocolate bars could be a sub-category under "plain dark chocolate" (meaning there are no added flavor inclusions); but if plain means ordinary, 100 percent cacao bars are usually anything but.
This bar had a slightly bitter, dark, forbidding chocolate aroma; and a fire-roasted dark flavor—but without the expected bitterness. It was, refreshingly, un-sweet, almost savory. A generous helping of cocoa nibs gave the bar a hearty, authentic cacao flavor and a crunchy texture.
One does need to work with very high-quality cacao for 100% chocolate, as there is nothing else to hide behind. No sugar, nothing else.
It's wonderful to see more 100% (no sugar) bars on the market over time that are actually enjoyable to nibble on. Montezuma's also offers their absolute black bars with flavors also (mint, orange, almond, etc.).