This Heart Healthy Beef Tartine features tender, balsamic-marinated sirloin steak layered over earthy, grilled mushrooms and finished with a bed of garlicky sautéed spinach. It’s a sophisticated, low-carb dish that works perfectly as an impressive appetizer or a light, protein-forward lunch. Traditionally, a tartine is an open-faced sandwich, and this recipe reinvents the classic by swapping bread for nutrient-dense portobello mushroom caps.
By using mushrooms as the "vessel" for the steak, you significantly reduce the carbohydrate count while adding a boost of antioxidants and fiber. The combination of chopped shallots and balsamic vinegar provides a bright, savory acidity that complements the richness of the beef without the need for heavy sauces or high-sodium seasonings. Be sure to check out all our hearty, healthy beef recipes if you’re hungry for more!
This recipe prioritizes lean protein and vegetable-based "grains" to support heart health and blood sugar management. By replacing traditional baguette slices with grilled portobello caps, you eliminate refined flours while increasing your intake of essential minerals and B vitamins.
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A tartine is simply an open-faced sandwich. In this healthy version, we use a portobello mushroom instead of bread to hold the beef.
Lean cuts like sirloin, flank steak, and tenderloin (filet mignon) are generally considered heart-healthy because they contain less saturated fat.
You can marinate the mushrooms and prep the spinach ahead of time, but for the best texture, we recommend grilling the mushrooms and steak just before serving.
While some beef tartines (like those using roast beef) are served cold, this grilled version is best served warm.
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Recipe yields 4 servings
Place the mushroom caps in a shallow dish. In a small bowl, combine 2 tablespoons of the oil, shallot, 3 cloves of the garlic and vinegar. Pour mixture evenly over the mushroom caps and let stand, in the refrigerator, for 1 hour or overnight.
Preheat grill to high. Grill the mushrooms for 10 minutes. Alternatively, preheat the oven to 400°. Line a baking sheet with foil or parchment. Roast the mushrooms for 10 minutes, flip and roast an additional 10 minutes. Cut the portobello caps in half. Set aside.
Season the beef with salt and black pepper to taste. Grill the beef for 2 to 3 minutes, flipping with tongs, or until desired doneness. Remove from heat and let rest.
In a skillet, heat the remaining 1 tablespoon oil over medium-high heat. Add the remaining 1 garlic clove and cook until fragrant, about 1 minute. Add the spinach and season with black pepper to taste. Sauté the spinach for 1 to 2 minutes, or until bright green and lightly wilted.
Slice the beef thin and arrange on the portobello mushroom slices. Top with spinach and serve warm.
While sirloin is excellent, you can also use lean flank steak or beef tenderloin. For a non-beef version, try thinly sliced grilled chicken breast.
If large portobellos aren't available, you can serve the steak on top of large, flat cremini (baby bella) mushrooms as "bite-sized" tartines.
Substitute the spinach with arugula for a peppery bite, or use sautéed kale for a heartier texture.
If you’re out of balsamic vinegar, red wine vinegar with a tiny pinch of stevia or honey can mimic that sweet-tart balance.