Sure. Undergarrison the province he's in.
This will lure the Almohads in attacking your 'inferior' army. This can be dangerous as it's a fine line between a seemingly inferior army and a effectively inferior army. You'll have use some good tactics and an excellent match-up to pull it of. A hint: use your jinettes (first all the javelins, later attack in flank or rear) to take on the AUM, the rest is more or less rabble.

One remark however, king Alphonso won't gain more command stars in battle as he is technically already defending when he remains in Spanish territories.