In a small skillet, toast the allspice and cumin over moderately high heat until fragrant, about 1 minute. Let cool. Grind in a spice grinder or mortar, or finely chop with a knife. Transfer to a bowl. Add the remaining 1/4 cup plus 1 tablespoon olive oil, the lemon juice, 1/2 teaspoon salt and a generous pinch of pepper.