To make the cabbage slaw, combine olive oil, vinegar, mustard and honey and whisk together. Taste and adjust as needed.
In a large bowl, toss together cabbage and carrot. Drizzle with dressing. Toss and evenly coat the cabbage mixture with dressing. If desired, you can also use your hands to slightly massage the dressing into the cabbage which will help soften it. Let it stand in fridge for about 30 minutes to one hour. Halfway through, mix again so that the bottom portions of the slaw that are soaking in the dressing at the bottom get moved to the top, helping to ensure that everything gets evenly mixed.
To build your taco, add some brisket to the center of your taco. Drizzle with BBQ sauce. Top with cabbage slaw. Add cilantro, cheese and a squeeze of fresh lemon juice.