Cover letters are the trailer to your resume (the feature film). And you want readers to feel like they've been invited to a star-studded premier, full of A-listers. Something they just can't WAIT to go to, I mean read.
If you have been in the workforce for a while, it is easier to extol your accomplishments, lead with one-liners and entice potential employers to review your resume. But if you have been out of the workforce, moms tend to err on the side of caution. They write cover letters that explain their absence from the workforce.
I wish - oh, how I wish - moms would stop explaining their extended leave of absence to raise kids as though they had the plague.
Write your cover letter as though you NEVER left. You aren't lying. If you have a gap on your resume, and are asked about it, be proud. Explain that you decided to stay home and raise 1, 2 3 or 18 beautiful kids (whatever the case may be) and had a marvelous experience. Discuss that you gained soft skills to add to your already robust repetoire. And remind your potential employer of your accomplishments - including those that occurred while working "at home".
When writing your cover letter, include accomplishments from BOTH your time AT work AND your time away from work. If you organized volunteer activities, led a girls scout troop, raised funds for a school event or volunteered at other social or community organizations - mention them. These things show initiative, organization skills, the ability to multi-task and leadership. Similar to your accomplishments when you worked full-time, be sure to include the IMPACT of your efforts. For example, you "managed a team of 8 people that developed and executed a strategy for servicing a local homeless shelter by raising $20,000,and developing relationships with local restaurants to deliver food items weekly that also reduced waste."
Please don't use your cover letter as a way of apologizng for staying home. Let your cover letter shine with ALL your accomplishments.