To soften hard cookie dough that has been refrigerated overnight before baking, there are a few methods you can try. Here are some suggestions:

1. Let it sit at room temperature: Take the cookie dough out of the refrigerator and let it sit at room temperature for about 15-30 minutes. This allows the fats in the dough, like butter, to soften, making the dough more pliable. Gently knead the dough with your hands to distribute warmth and encourage the fats to soften [1].

2. Microwave it cautiously: If you're in a hurry, you can use the microwave to soften the dough, but be cautious to avoid overheating it. Place the dough in a microwave-safe bowl and heat it on the lowest setting in short intervals. Check the dough after each interval and gently knead it to distribute the heat evenly. Be careful not to melt the fats in the dough, as it can affect the texture of the cookies [3].

3. Use a warm oven: Preheat your oven to the lowest temperature setting (around 170°F or 75°C) and turn it off. Place the refrigerated dough in a heatproof bowl or on a baking sheet and put it in the warm oven for a few minutes. The gentle heat will help soften the dough without melting the fats [1].

Remember, it's important to find the right balance between softening the dough and maintaining its structure. If the dough becomes too soft or the fats melt, it may affect the texture and spread of the cookies during baking. So, be cautious and monitor the dough closely during the softening process.

Learn more:

1. What is the best way to soften hard cookie dough that ... - Quora
2. Why You Should Refrigerate Cookie Dough
3. my cookie dough was in the fridge overnight and now its rock hard can I microwave it? - Seasoned Advice