For umami sauce, in medium saucepan, heat oil over medium and sauté garlic and ginger for 30 seconds to 1 minute, until fragrant. Whisk in maple syrup and tomato paste and cook for a few seconds. Slowly whisk in broth, vinegar, and tamari, and bring to a simmer. Simmer, uncovered, for 15 to 20 minutes, until thickened slightly. Continue to cook, uncovered, if a thicker sauce is desired. Store sauce in airtight container in the fridge for up to 2 weeks. Enjoy leftover sauce on grain bowls and steamed greens throughout the week.

For tartines, toast bread and place on warmed platter or plates. Spread each slice with mayonnaise and add avocado half to each slice of bread; smash avocado onto bread with fork, or thinly slice avocado and fan out. On top of avocado, add tomatoes, cut side up, followed by a drizzle of umami sauce and sprinkle of shichimi togarashi or sesame seeds. Serve immediately.