Heat another drizzle of olive oil in same pan over medium-high heat. Add shallot and a pinch of salt and pepper. Cook until fragrant, about 1 minute. Add tomatoes and cook, stirring, until slightly softened, about 1 minute. Stir in vinegar, stock concentrate, and ¼ cup water. Simmer until slightly thickened, 3-4 minutes. Turn off heat. Stir in 1 TBSP butter and any resting juices from beef.